[!!!][TASK] EXT:form - Use Extbase/ Fluid for frontend rendering

The form extension - including the custom data model, controller logic,
property validation, views and templating - has been adopted to support
the Extbase/ Fluid MVC stack. This allows better customization and
control of the generated behavior and markup by simply modifying Fluid
templates or utilizing own custom view helper logic. At the same time
the rewrite must not break current setups, i.e. the frontend rendering
must be as compatible as possible.

Resolves: #69401
Releases: master
Change-Id: Ieece008316417f70b54906221dbba4f9bcbf7f33
Reviewed-on: http://review.typo3.org/42927


Reviewed-by: Oliver Hader <oliver.hader@typo3.org>
Tested-by: Oliver Hader <oliver.hader@typo3.org>
Reviewed-by: Benni Mack <benni@typo3.org>
Tested-by: Benni Mack <benni@typo3.org>