Instructor dash changes for DOC-231, resequencing for DOC-230

Video: update acceptance test.

Fixed "ugettext" is imported as "_u" in lagacy dash.

LMS-2307

Release Notes for 3-18-14

mentoring-noworkbench: Remove import of workbench module (moved to SDK)

Video: Fix flaky acceptance test.

Kill the perfstats module, which is unused

Sarina/lms 1287

Mongo modulestore: create data dir

Make i18n tests quieter

We already have makedirs_p()

LMS-1287

LMS-1287

in create_user mgmt command, use settings.LANGUAGE_CODE instead of en-us

Fix split_test import and export.

Fixes the create_user admin command, which was creating user accounts
with a potentially invalid language preference.

JIRA: FOR-532

Add method to clear mako template lookups

LMS-2405

Ensure account creation succeeds before creating comments service user

Do not allow students to pin/unpin forum threads

Also improves handling in cases where account creation did succeed, but
comments service user creation did not.

Depends on commit 88abdd8a0b20bc9816f487b25abdea1953f5661d in https://github.com/edx/cs_comments_service

JIRA: FOR-522

refactor static tab tests