Updated SimpleTag & DataTag to have only "hasReference" & "removeReference" with "const string &id" parameter.
Fixed TestSimpleTag to use only "const string &id" version of "hasReference" & "removeReference"
Merge pull request #144 from balint42/fix_getter-setter

Final (alpha) fix of getter-setter patterns
removed todos and empty lines in Block.hpp
removed todo and minor cleanup in Property.hpp
setter for extents, positions and references changed to string versions

according changes to the Test, some more documentation
adding and removing References only with ids. added some documentation