Improve accessibility of forum vote buttons

Use <span> for course preview’s university #os

Fixing merge for sylvia's branch bld-615

Fixing merge for sylvia's branch bpd-615

Tests for behavior of export with & in HTML and XML-based components

Improvements to the i18n workflow tools.

Fix STUD-1129: handle out-of-range page numbers

Now any of the plurals being missing will count as an Empty translation,
and for looking at tags, the two English strings and all the translated
strings are mooshed together.

The tests in test_validate.py now examine the messages to see that they
have the right structure.  The English and the translation should have
the same tags, the translation can't be blank, and it can't have any
Astral plane characters.

Miscellaneous fixes to strings found during i18n work.

Assign valid content_type to static resource (import_static_content)

This change involves substantial refactoring of the relevant code to
reduce duplication. It also makes the templates for the vote buttons
more consistent and cleaner.

JIRA: FOR-64

A newer version was added to common/, so that is used instead. It is
also added to the set of JS files used in unit tests to allow forums
code in common/ to be tested.

Add info about template for Checkbox problem type

The course’s university was displayed using a <a> tag that points to
nothing ('#'). There was some stanford specific behavior to replace that
<a> tag with a <span>. This commit removes that.

Remove javascript_input and create_lti; add tools

Fix URI vendor module to be referenced via a relative URL.

Add more specific info about HTML+CSS+JS files, SOP

Django command to post submissions to ora

Don't catch all exceptions.

Modify server_track to handle being called without a request.

ORA-286

Add pagination to Studio's Files and Uploads page.

These changes are for STUD-813.

STUD-878

These changes implement STUD-813. The commit consists of the
following logical changes:
 - a REST API has been implemented for a course's assets
 - the page itself now fetches the assets client-side
 - the Backbone.Paginator library is used to support pagination
 - the AssetCollection has been refactored to extend
   Backbone.Paginator.requestPager so that it can be paged
 - an abstract PagingView class has been added to generalize
   the communication with a paging REST API
 - the AssetsView has been reimplemented to extend PagingView
 - two new child views have been added:
   - PagingHeader: the paging controls above the list of assets
   - PagingFooter: the paging controls below the assets