refactored Dom.addClass and Dom.removeClass to use Strings.addToList etc. functions
added test cases
Merge branch 'howling-mad' of github.com:alohaeditor/Aloha-Editor into hm-classes-refactoring
refactored usage of Dom.addClass
Merge pull request #1215 from cprerovsky/hm-classes-refactoring

Dom.addClass + Dom.removeClass refactoring