Part of STUD-847.

Added tests to video player controls to check new WAI-ARIA functionality. Added global custom Jasmine matcher to helper.coffee

[BLD-386]

BLD-426

The ErrorDescriptor wasn't getting the appropriate xmodule_runtime set,
and thus immediately raising an AssertionError when we tried to retrieve
and _xmodule from it.

[LMS-1388[

Fix bug when the user clicks on the video time-line either
before or after the specified end time, it jumps
to the very beginning of the video.

BLD-392

Read/Write inheritance split up into separate base classes

Fixes [BLD-456] and [LMS-1392], but making sure that we're always asking
XModules about their course_id (since the ModuleSystem has access to
that data).

mismatch

Adds a code block to the problem markdown parser that translates
[code]
TestTest
[/code]
to
<pre><code>
TestTest
</code></pre>

When a url contains a query parameter it gets incorrectly parsed
when replacing the /static portion.

This fix handles urls with query parameters.

Also let xml import work on modulestores that don't use write signaling

- Doubled up :hover and :focus styling to improve a11y
- Increase contrast of certain UI elements for improved a11y
- Added some image alt text for a11y
- Changed video caption styling to blue and made them underline on hover and added a skip link before video for screenreaders.

Fixes Bugs:
- LMS-1336

To help fix recent bugs re orphaned discussions and
to prototype a more restful json oriented api.