Implementation of the 'Library System'

Now there is a 'Base' type of some things like blocks and items wich
should be refered from Blocks. also they will be added to a Library
where they can be returned. Still very early implementation - more to
come... Furthermore in this commit I added a dedicated Creative tab,
made a example Block and Item for the new Library System and I removed
the testimage called 'PlayerInterface'. Github now fully mirrors my
actual code [15.11.14. - 21:30]