CONTENTBOX-381: Fixes with compat checks (+19 squashed commits)
Squashed commits:
[f076507] Removing unused files
[ab834c8] CONTENTBOX-381: Expand/collapse all; show errors
[876a08b] CONTENTBOX-381: Logic to not show menu items when inactive; interceptors to handle deletion of data and deactivation of menu items
[e5338d5] CONTENTBOX-381: Cleanup, added missing comments, etc.
[aa94700] CONTENTBOX-381: Added support for menus in main exporter/importer
[92e4557] CONTENTBOX-381: Small tweak for media callback
[d63d136] CONTENTBOX-381: Small tweak for media callback
[531ed86] CONTENTBOX-381: Added preview mode for editing interface; added interceptor to help with cleanup of menu hooks after various events in the application
[8daa0fd] CONTENTBOX-381: Provider cleanup and polish
[af7a4a7] CONTENTBOX-381: Provider cleanup and polish
[f952d37] CONTENTBOX-381: Added escape hatch in cb.menu() to prevent downstream self-nesting of menus (and thus infinite recursion...)
[99ddfc7] CONTENTBOX-381: Added widget for Menu
[6f2335e] CONTENTBOX-381: Finished menu renderer for CBHelper
[bd97d18] CONTENTBOX-381: Updates for import
[0ef7244] CONTENTBOX-381: Style cleanup, finished menu export
[9ba6337] CONTENTBOX-381: Finished persistence of menus
[b7c4759] CONTENTBOX-381: Start on menus
[b87f823] CONTENTBOX-381: Start on menus
[34923b9] CONTENTBOX-381: Start on menus
Merge branch 'dev-menus' into development
CONTENTBOX-490: Fixed typo in filebrowser
CONTENTBOX-381: Fixed broken "checkAll" checkbox