Fixes listing of other groups on individual group page on control panel.
Reinstates draggable selection on control panel.
Plays nicely with checkboxes.
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 #2161 from rtibbles/control_panel_fixes

Control panel fixes