[TASK] Base EXT: t3skin typography on Bootstrap

Adapt Bootstrap variables to well-known EXT:t3skin layout:
colors+gray, typography, paddings, table, buttons, inputs.

Use as much bullet-proof CSS of Bootstrap as possible:
Reduces inidividual CSS code in EXT: t3skin.

Resolves: #61568
Releases: master
Change-Id: Id5d6ea008692045f5b872fc13425fcb94caa5767
Reviewed-on: http://review.typo3.org/32751
Reviewed-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Tested-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Reviewed-by: Frank Nägler <typo3@naegler.net>
Tested-by: Frank Nägler <typo3@naegler.net>
Tested-by: Markus Klein <klein.t3@reelworx.at>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>