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

Split/branch settings LMS-11056
BLD-1104: List units that use group configuration.
REVERT THIS COMMIT BEFORE MERGE.