[TASK] Adapt BE module layout

Adapt the layout of BE modules to the style of TYPO3 CMS 6.2,
in particular use h1 for module title.

Also refactor the docheader into a partial.

Resolves: #57359
Releases: 0.6
Change-Id: I3533b111bd74755cd9a738912d34b3de22dc48c9
Reviewed-on: https://review.typo3.org/28896
Reviewed-by: Francois Suter
Tested-by: Francois Suter