[FEATURE] Configure CSS class as non-selectable in RTE

To filter some useless classes for authors, we can configure classes as
non-selectable in block or text style selectors.

Releases: master
Resolves: #58122
Change-Id: I6b151cf0524fccac6681a813b73f847783a69b95
Reviewed-on: http://review.typo3.org/29633
Reviewed-by: Stanislas Rolland <typo3@sjbr.ca>
Tested-by: Stanislas Rolland <typo3@sjbr.ca>