Hide playlists assigned in other units.
Adds unit for 'gift cards' for quiz points.
Linting.
Prevents teachers from altering units for other facilities.
Removes unit links on current unit page for all users.
Hides previous unit button for teachers.
Bumps query tests to account for additional database read for unit settings.
Fixes Unit related tests due to teacher changes.
Merge pull request #2498 from rtibbles/rct3_fixes

Client side Unit for Gift Cards and Restrict Displayed Playlists to Current Unit