[FEATURE] Base Buttons on Bootstrap - with compat layer

Bring default button style and base CSS definitions on Bootstrap
buttons. Brings backward compatibility for all buttons.

Resovles: #62392
Releases: master
Change-Id: I2cd59c00a649e65c03a7843e8de359e84baaa169
Reviewed-on: http://review.typo3.org/33469
Reviewed-by: Ingo Pfennigstorf <i.pfennigstorf@gmail.com>
Tested-by: Ingo Pfennigstorf <i.pfennigstorf@gmail.com>
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: Wouter Wolters <typo3@wouterwolters.nl>