[FEATURE] Use common classes for toolbar items

Create common CSS classes to be used for toolbar items so that it looks
the same, and extensions doesn't have to create the same css again and
again.

* Common "drop down" class
* Common ul/li definition
* Common layout, all looks the same

Change-Id: Iedad718ab4f26d87177e3d49ca93f58bf543d9f6
Resolves: #M17888
Reviewed-on: http://review.typo3.org/1088


Reviewed-by: Steffen Gebert <steffen.gebert@typo3.org>
Tested-by: Steffen Gebert <steffen.gebert@typo3.org>
Reviewed-by: Andreas Wolf <andreas.wolf@ikt-werk.de>
Tested-by: Andreas Wolf <andreas.wolf@ikt-werk.de>