[CLEANUP] Rewrite JS/HTML part of Flexform sections

* Adds a jQuery version of the JavaScript features
   for TCEform FlexForms, and include them in
   the TYPO3 rendering call when accessing
   TCEforms FlexForms.
 * Adds clean "t3-flex" prefixed CSS classes for all
   components of FlexForms sections. Added styling
   for the components with the new classes
 * Removes all existing inline JS code for FlexForms
 * Adds minor bug fixes (no title output for section
   elements, preview text will be rendered on load on
   hidden section elements)
 * Reviewed existing ACTION code in TCEmain
   for flexform elements

One minor side note is that sorting is not working, which
will immediately be replaced with jquery ui in a followup
patch.

Resolves: #38736
Releases: master
Change-Id: I9fadf06d3271dd771489fcdd182cddf9542b59fd
Reviewed-on: http://review.typo3.org/12698
Reviewed-by: Oliver Hader <oliver.hader@typo3.org>
Tested-by: Oliver Hader <oliver.hader@typo3.org>