Add mgmt cmd to generate anonymized ID mapping

Fix/adam/lms help button

Enable instructor dashboard in lms/envs/dev

Fixups to Nate's anonymized id mapper, repairing pep8 and pylint errors,
and rebasing on recent master.

So that instructors have easy access to the mapping from anonymized
IDs (a simple MD5 hash of the user ID that's used when integrating
with third-party services like Qualtrics) to user IDs, we have a
simple Django management command to generate a CSV mapping. To run,
use the following:

rake django-admin[anonymized_id_mapping,<system>,<env>,<course_id>]

And, of course, substitute the appropriate values for <system>, <env>,
and <course_id>. (E.g., lms, dev, and MITx/6.002x/Circuits)

remove unused code from xml_import.py

Changelog updates

Fix/adam/i18n templates

remove 'preview' from urls in enrollment emails sent while previewing a ...

Change course create form to asynchronous validation.

Change locators to a restful interface.

Fix error when there is an invalid YouTube property in a video module

Make descriptorsystem inherit from Runtime

Conflicts:
	cms/djangoapps/contentstore/views/preview.py

XBlock integration for Studio: student view

cleanup