CAPA problems have the "Staff Debug Info" button, which allows
instructors to "Reset Attempts" and "Rescore problem" for any individual
student.

XBlocks, such as Drag and Drop v2 do not support those, though the UI
was still present. Clicking any of those links would result in an
"Unknown Error Occurred" message.

This commit hides the two buttons if the associated block does not
support them.

[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.

- adaptation asides to be imported from the XML
- updating SplitMongo to handle XBlockAsides (CRUD operations)
- updating Studio to handle XBlockAsides handler calls
- updating xblock/core.js to properly init XBlockAsides JavaScript

Tests for xblock_utils.py functions.

- Remove escaping in display_name_with_default
- Move escaped version to deprecated display_name_with_default_escaped
- Does not include any other changes to remove double-escaping

Thanks to agaylard who initiated this work:
https://github.com/edx/edx-platform/pull/10756

TNL-3425

Staff markup was enabled on all block types in
https://github.com/edx/edx-platform/pull/10903

This works well inside the courseware, but it breaks layout of the course about
page, which is also an XModule, see:
https://github.com/edx/edx-platform/pull/10903#issuecomment-164266342

This commit disables staff markup/staff debug on all blocks except
blocks tagged with 'detached'. Detached blocks include course about
and info pages, static tabs.

TNL-2305

This allows course authors to choose between two difference licenses for their
course content: All Rights Reserved, or Creative Commons. In the backend, XBlocks
that wish to allow custom licenses need only inherit from LicenseMixin, which
adds a `license` field as a string.

License information is displayed in the Studio editor view, and just below the
rendered XBlock in the LMS. In addition, if the course block itself has a custom
license set, this license will display just below the main body of the page
on courseware pages.

This entire feature is gated behind the LICENSING feature flag.

The string "</script>" in JSON data would end the script element we're
embedding the data in.  To make sure the data doesn't disrupt the
script, we escape the slash as \/ .

[PLAT-217]

LMS-11235

[STUD-2903]

STUD-1754

STUD-1658

LMS-2737

This commit updates common/djangoapps.

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]

STUD-1558

[LMS-1645]
[LMS-2062]
[LMS-2063]
[LMS-2064]

Added feature setting 'DISPLAY_HISTOGRAMS_TO_STAFF' to configure display of histograms in Staff Debug Info panel.

Generating histograms requires scanning the courseware_studentmodule table on
each view. This can make staff access to courseware very slow on large courses.

Default is False.

LMS-1199