Add documentation of LMS/Studio features usable by XBlocks

[LMS-192]

JSON serialization error fixed.

Replace authz with roles.py and reconcile their behaviors

Fix typo in the announcement template

ORA-195

Verified Certificate Reports

Anton/fix negative exponents

Set default tolerance to 1e-3% for all responsetypes.

Anton/allow arbitrary regex in stringresponse

Refer to a ddt commit that actually exists (merging to unbreak master)

add FAQ link to course_about error msg

use double-quotes, not single

STUD-1006

Converted CONTRIBUTING to .rst

XBlock Xml Serialization/Deserialization

Internationalize forums CoffeeScript code

XModules continue to use their own interface for xml, but provide an
adaptor that makes the the XBlock interface available.

[LMS-179]

LMS: FIX - Add Styling Back to Certificate Download Button

small bugfixes for theming+sass+templates

Individual Due Date Extension feature

Adds a feature to the edX platform which allows instructors to set
individual due dates for students on particular coursework. This code is
meant primarily for on-campus use--it is not intended that this feature
would be used for MOOCs. It adds a new tab, "Extensions", to the beta
instructor dashboard which allows changing due dates per student. This
feature is enabled by setting FEATURES['INDIVIDUAL_DUE_DATES'] = True.

Copyright Notice Updates

Sarina/remove university refs