[BUGFIX] Form: Add more more semantic classes for elements

The system extension form renders elements with a wrapped class like
"csc-form-1" which just states the order or elements. To enable more
specific styling, a schema like the following is integrated:

csc-form-<id> csc-form-element csc-form-element-<type>

Change-Id: I0c03d047a757e8865f99b6200cc01bad19d06605
Fixes: #31561
Releases: 4.6, 4.7
Reviewed-on: http://review.typo3.org/6531
Reviewed-by: Georg Ringer
Reviewed-by: Philipp Gampe
Tested-by: Philipp Gampe
Reviewed-by: Oliver Hader
Tested-by: Oliver Hader