Implementing NYT's ICE track changes to Open Ended Assessements

Squashed commits to facilitate cherry-picking.  Committers and
original commit messages are:
- ==> @caesar2164, * ==> @jrbl, ~ ==> @jbau

- Added boolean to OE problem CMS settings to turn on ICE track changes
- Added ICE init and tracking start/stop to HTML
- Conditional in Peer Grading HTML for ICE container
- CSS styling for ICE container and insertion/deletion elements
- Added class to track changes HTML
- Added ice.min.js as well as included it in the js requirements for peer grading
- Use track_changes in peer_grading_problem
* Refactor peer_grading_problem to lookup track_changes variable by problem location.
* Whitelist ICE insert, delete tags
* Adds ICE multi-user-editor insert and delete tags to the peer grading sanitize_html whitelist.
- add reset button

* Introduction ICE means we need its inline tags to get passed through
  to the feedback target, but we don't want malicious peer feedback
  providers introducing <script>, etc, so we use lxml.html.clean to
  scrub peer grading input.
* Adds feedback URL autoheating.
* Allows ICE <insert> and <delete> tags but not others.

~ add helptext re: EXPERIMENTAL FEATURES

~ address a bunch of @VikParuchuri review comments on ICE for OEE
  ~ remove extraneous code
  ~ change to new xmodule accessors
  ~ refactor filtering

~ fix broken test test_peer_grading_problem

~ Create track_changes.coffee and remove <script> from
  peer_grading_problem.html
~ Remove all reliance on id in favor of local scoping and classes

~ bring up test coverage somewhat

~ remove superflous $.scrollTo

~ TODO: Filtering

Add mixins to XModuleDescriptors as they are loaded during xml parsing

keep-bson-in-mongo-code

Conflicts:
	common/lib/xmodule/xmodule/modulestore/mongo/draft.py
	lms/djangoapps/courseware/tests/modulestore_config.py

Hotfix 09/13/2013

Don't try and modify the location proproperty

fix-setattr-and-getattr

Jarv/grade dump

Send JSON messages to Software Secure in UTF-8, without escaping

LMS: Header Logo/Brand alt Attribute Value Fix

Verification: Copy/Instruction Edits

Make URL patterns to exclude from tracking configurable

Add ARIA dialog role to Markdown editor dialogs

Show order errors in page instead of in an alert.

Fix/vik/pg hotfix

Small fixes for unicode

fix default for VERIFY_STUDENT in lms/envs/aws.py

* Add unit test coverage for this "exclusion from tracking" logic
* Exclude based on regex match instead of raw string comparison
* Exclude heartbeat requests from tracking

Help Modal - Accessibility Fixes

Conflicts:
	common/lib/xmodule/xmodule/tests/test_peer_grading.py

Verification Process: Copy Changes