Getting draft split_test_module instances to import/export.

STUD-327
Added text about grade ranges and certificates
Merge pull request #4529 from edx/markhoeber-documentation-doc420

Added text about grade ranges and certificates
Merge pull request #4491 from edx/christina/export-split

Getting draft split_test_module instances to import/export.
Release notes for 7-23-2014
Merge pull request #4531 from edx/sylvia/docs/relnotes_7_23

Release notes for 7-23-2014
Make overriding branch settings thread-safe LMS-11125
Merge pull request #4494 from edx/nimisha/request-cache-for-branch-settings

Make overriding branch settings thread-safe LMS-11125
Split branch settings LMS-11056
Bugfix: Initialize new tabname to "Empty"

In Studio, when the course administrator creates a new tab, its name was being
initialized as null in the mongo database. This caused students in LMS to get a
server error when trying to access the course page, since LMS was trying to
process the null tabname for translation, etc. Now tabname is initialized as
'Empty', which is how it was being done in the frontend.

STUD-2000
Split branch settings code review fixes LMS-11056
Merge pull request #4532 from edx/split/branch-settings

Split/branch settings LMS-11056
BLD-1110: Create, edit, delete groups.
Add correct_or_past_due option for showanswer and update relevant documentation
Add Martin Segado to authors file
Merge pull request #4480 from edx/anton/create-edit-delete-groups

Group Configuration: create, edit, delete groups
Add support for theme translations and LANGUAGE_DICT override
Improvements to clicking and synchronization in Studio bok-choy tests.
Merge pull request #4209 from msegado/showanswer-correct-or-past-due

Add "Correct or Past Due" option for showanswer
Merge pull request #4533 from Stanford-Online/kluo/i18n-support-theme

Add support for theme translations and LANGUAGE_DICT override