new label-oriented interface in IBookCollection
BookCollection sends label to db
Merge branch 'master' into beta

Conflicts:
	src/org/geometerplus/android/fbreader/libraryService/BookCollectionShadow.java
	src/org/geometerplus/android/fbreader/libraryService/LibraryService.java
	src/org/geometerplus/fbreader/book/BookCollection.java