[TASK] Documentation extension cleanup #2

Moved templates and layouts to proper place
Changed repository to not extend default repository
[TASK] Documentation extension cleanup #3

Changed vendor namespace from TYPO3CMS to TYPO3\CMS
[TASK] Extension documentation cleanup #4

Removed files related to deleted "variant" model.
[BUGFIX] Invalid Backend module registration
Merge pull request #1 from fsuter/master

Update from fsuter