adding maya to supported distro list for create-dev-env.sh

Added tooltip styles, made all buttons the same, and other small changes...

add course enrollment windows

Feature/fix replication side effects

* if the course metadata have enrollment_start and/or enrollment_end,
  only allow normal users to enroll post start and pre end.
* If DARK_LAUNCH is on, staff can enroll outside the window

1. Multiple save()s on the same model are now handled properly. We
   had to unmark model objects after the appropriate signals had
   fired.
2. There was a side-effect where we were saving the portal User
   object to the course_db with the using kw param, but models
   remember where they were last saved to, so a later save on that
   model object would go to the wrong database.

Feature/tomg/fall design

Partial scoring

Adding a javascript-based response type

Conflicts:
	common/lib/xmodule/xmodule/js/src/capa/display.coffee
	common/lib/xmodule/xmodule/tests/__init__.py
	common/lib/xmodule/xmodule/x_module.py
	lms/djangoapps/courseware/module_render.py

Provide content QA (quality assessment) interface

Model replication to course databases

Conflicts:
	lms/urls.py

Hide errors from non-staff users

Feature/victor/bad content warn not error

Feature/victor/dark launch

Sketchy adding of test dbs to the cms test.py config file -- these are required for the Student (shared django app) tests to run