[TASK] Make file_edit.php dispatched

Use dispatching for file_edit.php

Resolves: #56743
Releases: 6.3
Change-Id: Ib25745dd29642a83aa5700752c83cda8e11ea7fa
Reviewed-on: http://review.typo3.org/28238
Tested-by: Helmut Hummel <helmut.hummel@typo3.org>
Reviewed-by: Helmut Hummel <helmut.hummel@typo3.org>