get the raw DescriptorSystem, not the CombinedSystem when instantiating xmodules (TNL-1226)

quality fixes

remove trailing comma

returns XBlockuser with 2 data layers

PLAT-280

PLAT-221

[PLAT-217]

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

Lots of plumbing to allow an asset named python_lib.zip to be imported
by jailed Python code.

This function can find the "python_lib.zip" asset, and is passed down
through ModuleSystem and LoncapaSystem so that capa problems have access
to the zipfile.

[STUD-2903]

STUD-1754

STUD-1948

This reverts commit a16f5487.

STUD-1658

[LMS-2757]

STUD-1312

This commit implements STUD-1490, allowing creation of components
on the container page. It also enables the delete and duplicate
buttons now that new content can be created that would benefit.

Note that it also creates shared functionality for adding components,
and refactors the unit page to use it too.

This commit adds all of cms.

These keys are now objects with a limited interface, and the particular
internal representation is managed by the data storage layer (the
modulestore).

For the LMS, there should be no outward-facing changes to the system.
The keys are, for now, a change to internal representation only. For
Studio, the new serialized form of the keys is used in urls, to allow
for further migration in the future.

Co-Author: Andy Armstrong <andya@edx.org>
Co-Author: Christina Roberts <christina@edx.org>
Co-Author: David Baumgold <db@edx.org>
Co-Author: Diana Huang <dkh@edx.org>
Co-Author: Don Mitchell <dmitchell@edx.org>
Co-Author: Julia Hansbrough <julia@edx.org>
Co-Author: Nimisha Asthagiri <nasthagiri@edx.org>
Co-Author: Sarina Canelake <sarina@edx.org>

[LMS-2370]

JIRA: FOR-429

STUD-1306

STUD-1363

This is the changes for STUD-1244, which introduces the ability for Studio to display
arbitrarily nested xblocks. In this change, a new container page is introduced which can
display nested xblocks. In particular, the xblock type of 'vertical' is special cased
to be shown inline as a collapsible section. The unit page is mostly unchanged, except
that container xblock's are shown as a link to their container page, rather than being
shown inline.

To get all dates localized, we need all runtimes to have the i18n
service, and since runtimes are made by the modulestores, we need to
pass it to them.

Soon (fingers crossed), modulestores won't be involved in making
runtimes, and many of these changes will go away.

This requires fixing the javascript api implementation, and adding
an implementation of get_block to the ModuleSystem api.

However, the implementation is incomplete, due to mismatches between
the expectations of XModule and XBlock.

Also adds tests using the Acid block to make sure that the javascript
and python apis for children are working correctly.

STUD-967

[LMS-1421][LMS-1517]

Make XBlock client-side runtimes proper classes, so that handlerUrl can
be defined in a per-runtime way, and we can have multiple runtimes on a
single page.

[LMS-1630][LMS-1421][LMS-1517]

fixing unit tests

fixing merge error

fixing xqueue submission issue with unicode url (trial 0.1)

fixing fotmats as commented upon

removing yaml file language selection

Unicode changes to support QRF

removed unnecessary pass in modulestore/init.py

fixing merge error

fixing fotmats as commented upon

removing yaml file language selection

fixing pep8 violations

- fixing pylint violations

pylint violation

fixing line spaces and formats

ignore pylint E1101

remove empty line

fixing pylint violations

 pep8 violations

bulk mail unicode/decode

fix migration error

fix pep8 just to push again

more unicode/decode
Final changes to comments and error messages.