Merge pull request #2160 from aronasorman/delete-group-tests

Delete group tests
Reinstates draggable selection on control panel.
Plays nicely with checkboxes.
Fixes linting.
in tests: wait longer for the facility or group deletion to happen
Comment out hidden divs to fix alignment issue on tabular report for firefox
add modifymodel mgmt command
Adds test for session timeout.
Fixes pct_mastery for groups to show %, not fraction.
Merge branch 'release-0.12.0' of github.com:learningequality/ka-lite into release-0.12.0
Merge branch 'release-0.12.0' into control_panel_fixes
Fixes button disabled toggling.
Prevents 'Ungrouped' from being selected in group control interface.
Fixes bug that hid coaches if no groups in facility.
Merge pull request #2159 from rtibbles/session_timeout

Timeout Django sessions
Merge branch 'nalanda-rct2' into feature/2122-Exam-list-page
Initial unit tests for `student_testing` app for the #2151 - Exam list page story.
Initial unit test to redirect student if exam mode is on based on browser post, tastypie api put call, or value was set at database.
Backbonify PlaylistTableView in homepage
Merge pull request #2162 from dylanjbarth/align_tables

Align tables in firefox
Merge pull request #2161 from rtibbles/control_panel_fixes

Control panel fixes
Merge pull request #2157 from heidimason/scratchpad-boundary-fix

Scratchpad boundary fix