Adding more classes (including support for config-based facet groups)

This is related to https://github.com/GigaOM/legacy-pro/issues/4155, but doesn't need to wait for the actual styling to get pushed.

Done with @Camwyn
Removing silly title_class
Merge pull request #53 from borkweb/4155-add-more-classes-to-widget

Adding more classes (including support for config-based facet groups)