Merge pull request #2281 from learningequality/release-0.12.0

Release 0.12.3
metadata for 0.12.3
Merge branch 'release-0.12.0'
Merge pull request #2308 from learningequality/release-0.12.0

Release 0.12.5
Merge pull request #2351 from learningequality/release-0.12.0

Release 0.12.6
cleanup student_testing/tests.py imports
extend KALiteTestCase to have a default device now. Fix some MRO errors because of inheriting CreateDeviceMixin
create a KALiteClientTestCase and a skeleton KALiteBrowserTestCase
fix CurrentUnitTests and CoreTests inherit from KALiteTestCase
started cleaning up and removing CreateDeviceMixin
don't launch pdb when --failfast is given as parameter
start refactoring tests to use BrowserActionMixins and the new KALiteBrowserTestCase
make kalite.distributed tests work by using a combination of BrowserActionMixins, FacilityMixins and KALite*TestCase
make kalite.student_testing tests work
make kalite.i18n tests work
make kalite.control_panel tests work
fix kalite.coachreports tests
fix kalite.updates tests
clean up imports in main/tests/base.py
Add link to coach ungrouped students.