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

Skipped 'print' statement violations, as print() is Py3k syntax.

Import asset metadata XML into modulestore.
Optimize importing many items of asset metadata by avoiding multiple
round-trips to MongoDB.

Remove post-publish step.

LMS-2950 move delete_course to Mongo.

Refactor get_parent_locations STUD-1663

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]

Currently if a course is only imported from the command line the
forum permissions are not seeded, this adds that functionality
Switched to doing seeding outside of xmodule library
Switched to using course_items
Switching to simpler test class

For seeing overview of system status, for deleting and loading
courses, for seeing log of git imports of courseware.  Includes command
for importing course XML from git repositories.

Added a lot of tests for additional coverage with some minor fixes
those tests discovered

and without rewriting static links.  changes xml_importer.py and
import.py

Add Draft module store that is used whenever any item is update in the CAS (but not during import, and not for templates)

Make imports into the CMS ignore broken modules, while still loading bad xml as error modules in the LMS

Acknowledge the fact that right now keystore is really just a module store. If we need a keystore that returns other objects, we can reexctract the base class into it's own module again

Make location into a named tuple, and use it more as a first class entity, rather than URL for identifying content

Move the resources_fs abstraction into the primary DescriptorSystem, as it is needed for more than just XMLParsing

Revert "Make import work via mako again, to unblock others while I work on making the LMS work using XModuleDescriptors"

This reverts commit 6fdf44fe.

Make import work via mako again, to unblock others while I work on making the LMS work using XModuleDescriptors