[FOLLOWUP][TASK] Decouple t3editor hooks from DocumentTemplate

Clean up calling code as well.

Releases: master
Resolves: #70387
Change-Id: I04a542c02f353db1052aed646e7537d47a80d8df
Reviewed-on: http://review.typo3.org/43825


Reviewed-by: Mathias Schreiber <mathias.schreiber@wmdb.de>
Tested-by: Mathias Schreiber <mathias.schreiber@wmdb.de>
Reviewed-by: Helmut Hummel <helmut.hummel@typo3.org>
Tested-by: Helmut Hummel <helmut.hummel@typo3.org>