[LMS-2757]

This commit adds the non-courseware lms/djangoapps and lms/lib.

These keys are now objects with a limited interface, and the particular
internal representation is managed by the data storage layer (the
modulestore).

For the LMS, there should be no outward-facing changes to the system.
The keys are, for now, a change to internal representation only. For
Studio, the new serialized form of the keys is used in urls, to allow
for further migration in the future.

Co-Author: Andy Armstrong <andya@edx.org>
Co-Author: Christina Roberts <christina@edx.org>
Co-Author: David Baumgold <db@edx.org>
Co-Author: Diana Huang <dkh@edx.org>
Co-Author: Don Mitchell <dmitchell@edx.org>
Co-Author: Julia Hansbrough <julia@edx.org>
Co-Author: Nimisha Asthagiri <nasthagiri@edx.org>
Co-Author: Sarina Canelake <sarina@edx.org>

[LMS-2370]

Part of STUD-1030

- require confirmation when clicking Open Ended reset button (now working)
- require confirmation when submitting Open Ended essay (now working)
- disable text feedback area during calibration and let users know that they should give feedback when grading
- fixed error message typos

This reverts commit 3b29d605.

- require confirmation when clicking Open Ended reset button
- require confirmation when submitting Open Ended essay
- disable text feedback area during calibration and let users know that they should give feedback when grading
- fixed error message typos

A somewhat working state for notifications.  Combined open ended and peer grading xmodules still have significant errors.