[PERF-303] Integer XBlocks/XModules into the static asset pipeline.

This PR, based on hackathon work from Christina/Andy, implements a way to discover all installed XBlocks and XModules and to enumerate their public assets, then pulling them in during the collectstatic phase and hashing them.  In turn, the methods for generating URLs to resources will then returned the hashed name for assets, allowing them to be served from nginx/CDNs, and cached heavily.

* mattdrayer:  Latest proto code
* mattdrayer:  Add translation.py
* asadiqbal08: Xblock translation ugettext update, remove translation.py
* mattdrayer:  Additional I18N work -- starting to see some translations!
* asadiqbal08: Trying to make xBlock message catalog files path dynamic
* mattdrayer:  Remove unnecessary modifications
* mattdrayer:  Cleaned up implementation
* mattdrayer:  Moved import statement
* asadiqbal08: update as suggested
* asadiqbal08: xblock its own domain
* asadiqbal08: translation: secure none object
* asadiqbal08: pylint
* asadiqbal08: get locale from xblock
* asadiqbal08: update
* mattdrayer:  Determine XBlock locale path within runtime service
* mattdrayer:  Determine module location via the runtime
* mattdrayer:  Remove ModuleI18nService reference
* asadiqbal08: override the service in studio
* asadiqbal08: remove import
* asadiqbal08: update the Modulei18nService
* asadiqbal08: update the Modulei18nService
* mattdrayer:  Remove redundant __class__ reference
* asadiqbal08: update the docstring
* asadiqbal08: tests
* mattdrayer:  Remove specific ugettext override from ModuleI18nService
* mattdrayer:  Move service operation to base class
* mattdrayer:  Address quality violations
* asadiqbal08: Investigating the test failure issue on jenkins and solved
* asadiqbal08: First utilizing the parent class method
* mattdrayer:  Use recommended callable approach
* asadiqbal08: remove unused code
* asadiqbal08: Updated the test to use cms preview module system runtime in order to get i18n service.
* asadiqbal08: Pylint quality
* asadiqbal08: update the service call to check xblock declarations
* asadiqbal08: update doc string
* asadiqbal08: i18n callable test in studio
* asadiqbal08: test lms runtime for modulei18n service
* asadiqbal08: add doc strings
* asadiqbal08: Rename locale and domain to Flask-Babel convention

ECOM-2678

Also remove its corresponding ACCESS_REQUIRE_STAFF_FOR_COURSE feature
flag.

There are English words in these strings, but they are actually specific
values that must appear as these English words, and so should not be
translated.

Please note that this is a squshed commit and the work of:
Symbolist, macdiesel, nedbat, doctoryes, muzaffaryousaf and muhammad-ammar

Replaces instances of an old hack with the more clear ugettext_noop.

* The LMS now also monkey-patches
  xmodule.x_module.descriptor_global_handler_url and
  xmodule.x_module.descriptor_global_local_resource_url so that we can
  get LMS XBlock URLs from the DescriptorSystem. That functionality is
  needed in the block transforms collect() phase for certain XModules
  like Video. For instance, say we want to generate the transcripts
  URLs. The collect phase is run asynchronously, without a user context.

* The URL handler monkey-patching is now done in the startup.py files
  for LMS and Studio. Studio used to do this in the import of
  cms/djangoapps/contentstore/views/item.py. This was mostly just
  because it seemed like a sane and consistent place to put it.

* LmsHandlerUrls was removed, its handler_url and local_resource_url
  methods were moved to be top level functions. The only reason that
  class existed seems to be to give a place to store course_id state,
  and that can now be derived from the block location.

* To avoid the Module -> Descriptor ProxyAttribute magic that we do
  (which explodes with an UndefinedContext error because there is no
  user involved), when examining the block's handler method in
  handler_url, I made a few changes:

** Check the .__class__ to see if the handler was defined, instead of the
   block itself.

** The above required me to relax the check for _is_xblock_handler on the
   function, since that will no longer be defined.

90% of this goes away when we kill XModules and do the refactoring we've
wanted to do for a while.

* Automatically create user partitions on course publish for each ICRV checkpoint.
* Disable partitions for ICRV checkpoints that have been deleted.
* Skip partitions that have been disabled when checking access.
* Add verification access control UI to visibility settings.
* Add verification access control UI to sequential and vertical settings.
* Add partition scheme for verification partition groups.
* Cache information used by verification partition scheme and invalidate the cache on update.
* Add location parameter to UserPartition so the partition scheme can find the associated checkpoint.
* Refactor GroupConfiguration to allow multiple user partitions.
* Add special messaging to ICRV for students in the honor track.

Authors: Zubair Arbi, Awais Qureshi, Aamir Khan, Will Daly

This reverts commit 4312c0e7.

TNL-1493

See https://openedx.atlassian.net/wiki/display/TNL/User+API for details

xblock-external-ui: Include CSRF token in the API answer
xblock-external-ui: Include full path when building local_url
xblock-external-ui: Fix TestHandleXBlockCallback & bok_choy, add tests
xblock-external-ui: Only return `instance` in `_invoke_xblock_handler()`
xblock-external-ui: Group resources by hash tag to avoid duplicate loads
xblock-external-ui: PEP8
xblock-external-ui: Fail early if the XBlock view is called anonymously

    We used to serve anonymous requests, but most XBlocks assume that the
    user is logged in, which can generate a lot of errors when the user is
    accessed or when an XBlock ajax callback is queried. Fail early to only
    get one error per page load, and prevent displaying the XBlock
    altogether when the LMS doesn't find an active user session.

xblock-external-ui: Add request params in view render context
xblock-external-ui: HTTP error status when file is too large for handler
xblock-external-ui: Fix unicode encodings in XBlock rendering
xblock-external-ui: Feature flag for API call ENABLE_XBLOCK_VIEW_ENDPOINT

TNL-652

TNL-498

PLAT-280

PLAT-221

[PLAT-217]

Move lms.lib.xblock into lms.djangoapps.lms_xblock in preparation add database backed configuration to it