This reverts commit 544616be.

Restore reverted changes from paver part 1

This reverts commit df2e410f.

Deprecated rake functions issue a warning and then call paver
replacements

Bring Paver commands up to date with master for servers, assets, and docs.
Revert deprecation of quality, tests, and i18n for a future pull request.
Deprecate workspace migration

Provided several suggestions what to do if MongoDB
daemon doesn't start.

STUD-1094

Using `ulimit -n` to set the limit much higher than the default of 256
in Darwin seems to avoid the `EMFILE` error that was plaguing our Mac
developers.

Fixed mistake in pip install snippet

* All access control logic is now in access.py
* It exports a single method for general use: has_access(user, object, action)
 - possible actions depend on object type (e.g. 'see_exists', 'enroll', 'staff')
* Removed DARK_LAUNCH feature flag--it is now the default behavior
* Replaced check_course with three separate more focused functions that use has_access

Minor things:
* note on using pdb in testing
* moved time parsing helper into timeparse.py
* x_modules now have a .start attribute (None if not in metadata)