Compatibility: Add BS4 compatibility to the Slider cell. Compatibility: Use the proper Views API to get available Views and WordPress Archives, instead of querying. Compatibility: Solve some visual glitches with the new styling on WordPress 5.3. Performance: Do not define templates for layout cells outside a layout editor. Performance: Cache the list of layouts available for assignment. Bug-fix: Fix an issue when trying to assign a layout to a post being saved inside the save action of another post.
Performance: Cache whether the current theme is integrated, to avoid checking every time.
Fix the menu cell when using BS3. Fix an issue with the OTGS/UI dependency caused by a missing file.
