Escape ampersand characters to the corresponding entity in the `Versions` class

Signed-off-by: xchs <github@gmx.net>
Add the `FilesystemIterator::SKIP_DOTS` flag
Correct the phpDoc of the `Dbafs` class and a changelog entry
Merge pull request #5581 from xchs/fix-amp-escape
Add the `Model::postSave()` method
Tangible file synchronization performance improvements
Show the file picker radio buttons in the style sheet editor (see #5586)
Show the file picker radio buttons in the theme editor (see #5582)
Fix the file picker (see #5574)
Fix the grid column width reset on mobile devices (see #5584)