Style der Buttons an einer Stelle definiert

- Optische Anpassungen
Fehlenden Hover hinzugefügt
rebase branch 'luhcas/master' from #174 onto the master branch

Conflicts:
	blocks/Courseware/css/courseware.css
	blocks/Section/css/section.css
transform changes in CSS files from f28eafe and eae7f7b to the LESS files
Merge pull request #182 from xabbuh/button-style-merge

Verbesserung der Buttonstyledefinitionen