[FEATURE] Monochrome action icons (FontAwesome)

Slot for IconUtility to hook into sprite icon generation.
Delivers monochrome action icons.

"Action icons start actions right with the first click."
Documentation for Iconography in #62158.

Related: #62158
Resolves: #49955
Release: master
Change-Id: I24b1a160b983d690567ad5ba015c6bf13af4f403
Reviewed-on: http://review.typo3.org/33285
Reviewed-by: Ingo Pfennigstorf <i.pfennigstorf@gmail.com>
Tested-by: Ingo Pfennigstorf <i.pfennigstorf@gmail.com>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>