[FEATURE] Refactor EXT: t3skin CSS to Less & variables

Make use of Less hierarchy and constraints. Dissolves "visual" and
"structure" folders in order to use Less variables for "Visual"
layout at a later point.

This patch:
+ moves Less files
+ merges visual and structure sub-folders
+ merges several CSS classes into hierarchical format.

Patch explicitly does not yet:
+ refactor CSS definitions
+ removes duplicated CSS definitions
+ make use of Bootstrap where applicable.

Layout in the backend before and after this patch does not change.

Resolves: #62042
Releases: master
Change-Id: Ic9045a565c3a81808431c217379ffb375807c071
Reviewed-on: http://review.typo3.org/33170
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>
Tested-by: Georg Ringer <georg.ringer@gmail.com>
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: Wouter Wolters <typo3@wouterwolters.nl>
[TASK] Remove styling code in FormEngine/TCA

FormEngine uses a combination
of classes and styles, which is very
complicated and not usable. A new way
of handling the styling is needed.
All old methods are deprecated and not in use
anymore.

At a later step, proper classes can be introduced
and styling can be done in LESS cleanly
without any PHP magic.

Releases: master
Resolves: #61890
Change-Id: Ie72226e1c6d795b3d8b53220fbcbee9e059935a6
Reviewed-on: http://review.typo3.org/32975
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: Wouter Wolters <typo3@wouterwolters.nl>
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>
Tested-by: Georg Ringer <georg.ringer@gmail.com>
Reviewed-by: Benjamin Mack <benni@typo3.org>
Tested-by: Benjamin Mack <benni@typo3.org>
[CLEANUP] Always use HSC in TS labels in BE

The ExtendedTemplateService class contains
a switch "ext_noSpecialCharsOnLabels" which
is never used in the core. It is used to call a wrapper
function that simple doesn't do HSC() if the
option is set.

The method and option can be deprecated.

Releases: master
Resolves: #61513
Change-Id: I90e1f3728287b9f4dfa93f4cfc6875b5314a0eb3
Reviewed-on: http://review.typo3.org/32707
Reviewed-by: Markus Klein <klein.t3@reelworx.at>
Tested-by: Markus Klein <klein.t3@reelworx.at>
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>
Tested-by: Georg Ringer <georg.ringer@gmail.com>
[BUGFIX] Buttongroup for icons in toolbar not floated to the left

Fix a left over for removing styles which were missed in #61890

Resolves: #62064
Releases: master
Change-Id: I8121e901986cfa40388eba53f073184dc9b7f317
Reviewed-on: http://review.typo3.org/33176
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>
Tested-by: Georg Ringer <georg.ringer@gmail.com>