started implementing Unpacking
implemented context menu for BackPackSoundFragment
unpacking works regarding to copying the file
beginn to implement garbage collector for backpack
refactoring regarding to garbage collector
implemented garbage collector- needs prove
Garbagecollector and Unpacking works
implemented tests for unpacking
small adaptions regarding to implementation and testing
implemented backpackflag
merged with master
Acceptance changes
(squashed)
Merge pull request #764 from Catrobat/gsocBackPackPaste

Gsoc back pack paste
Squashed into 8 commits (there was a merge commit in between - in future git rebase master should be used instead of merge master).