Allow extra fields returned from comments service

Previously, an error was raised if the comments service returned data
including an unexpected field, which unnecessarily complicated the
release path for new features, since the list of allowed fields would
need to be modified before cs_comments_service could be modified, and
only then could edx-platform take advantage of the new CS feature. We
still log a warning if an unexpected field is returned, so we will
still be able to tell if the CS returns a corrupt response.

JIRA: FOR-180
Merge pull request #3601 from edx/markhoeber/documentation/doc-331

Release Notes for 5-6-14
Release notes date fix
Merge pull request #3686 from edx/markhoeber/documentation/release-notes-date-fix

Release notes date fix
Pass deprecated course keys through
Merge pull request #3647 from edx/gprice/comment-client-allow-extra-fields

Allow extra fields returned from comments service
Fix failing tests
Make Locators comply with UsageKey accessors
Merge pull request #3687 from edx/flowerhack/fix-discussion-opaque

Flowerhack/fix discussion opaque
Simple fixes

- Ensure temp files are cleaned up.
- Refactor a function with three return statements.
add max-attempts to inheritance.py (LMS-2130)
fix importing bug (STUD-1599)

add target_location_namespace check
fix staff_grading server error
Merge pull request #3530 from edx/dhm/opaque-locator

Make Locators comply with UsageKey accessors
Add my name to the authors file
Fix #3347: "Run Code" reloads page in Matlab Problem

Instead of refreshing only the necessary parts,
"Run Code" reloads the whole page.

This commit fixes this behaviour, by refreshing the
specific elements belonging to the Problem instead.

Also tidies up indentation.
Remove calls to loc_mapper
Merge pull request #1 from edx/ned/tweaks-for-pr-3464

Simple fixes
Merge pull request #3664 from edx/adam-inherit-max-attempts

add max_attempts to inheritance.py (LMS-2130)
Merge pull request #3626 from edx/adam/fix-import-bug

fix importing bug (STUD-1599)