Adding ability to give an attribute callback for CAS
Certificates: Additional flags for regenerate_user

* -G allows explicit setting of grade condition (e.g., a string such as
  'Distinction', 'Pass', 'F', 'B') for the certificate, regardless of
  grader output for the user.
* -T allows explicit request of a particular certificate template to be
  applied to a given user's certificate regeneration, i.e.:
    -T doctor_distinction.pdf
  to generate a certificate of distinction for doctors.
added loading pattern to studio
Fix incorrect parse of url in video_module.py

Sometimes the video url may look like 'http://abc.com/path/video.mp4?xxxx'.
(For example, the Windows Azure's media service will offer such type of url.)
The original code in video_module.py will produce 'mp4?xxxx' instead of 'mp4'
as the extension of a filename for such type of url, and therefore the video
will be non-playable. The fix here uses the built-in urlparse module to retrive
only the path component from a url and therefore the extension 'mp4' will be
correctly fetched.
Puts module.render() in try statements.

LMS-1192
BDL-810: Fix image mapped inputs.
Simple email checking for batch enrollment on inst dash

LMS-2244
Fix acceptance test.
use unicode strings for slug and regex
STUD-1433
Fixed email in authors.txt
Removed unused code that is over 2 years old.
Merge pull request #2992 from edx/sarina/fix-beta-batch-enrollment

Simple email checking for batch enrollment on inst dash
Merge pull request #3001 from edx/anton/fix-flaky-acceptance-test

Video: Fix flaky acceptance test.
Merge pull request #2988 from edx/anton/fix-multiple-image-inputs

Fix image mapped inputs.
Merge pull request #2925 from edx/zub/bugfix/std1433-importunicodename

use unicode strings for slug and regex
Merge pull request #3007 from edx/frances/feature/ui-loading

added loading pattern to studio
Merge pull request #3011 from edx/valera/delete_old_files

Removed unused code that is over 2 years old.
Fix the url processing error when there is a query string inside the video source's url

1. In video_module.py, rewrite the get_ext() function to use the built-in urlparse module to parse the input filename first and then get the file's extension name from the parsed path.
2. In test_video.py, add two test cases (one with query string while the other without) in order to test the rewritten get_ext() function.
Merge pull request #2963 from louyihua/master

Fix incorrect parse of url in video_module.py
Commenting out a flaky acceptance test.