synchronization with library-service branch + constants are moved from Library to LibraryTree
Merge branch 'master' into ice-cream-sandwich
introduced BookWithAuthorsTree class
Merge branch 'master' into ice-cream-sandwich
synchronization with library-service branch
Merge branch 'master' into ice-cream-sandwich
AuthorListTree
Merge branch 'master' into ice-cream-sandwich
synchronization with library-service branch
Merge branch 'master' into ice-cream-sandwich
synchronization with library-service branch
Merge branch 'master' into ice-cream-sandwich