Added missing exception class
Merge branch 'master' of git@github.com:mrgimo/mixtape-core.git

Conflicts:
	src/main/java/ch/hsr/mixtape/application/FirstRunException.java
Bugfixes and more functions in PlaylistService; Implemented logger; Refactorded DummyData-Generator; Introduced some Exceptions;
Merge branch 'master' of git@github.com:mrgimo/mixtape-core.git