Added tests for MARMOTTA-221, MARMOTTA-197
new Selector: GroupedSelector, to avoid loosing brackets on re-serialisation
(fixes MARMOTTA-197)
On serialisation, nodes can also be Literals
fixes MARMOTTA-221
Brackets now have to be added explicitly.
Fixed some tests in ldpath parsing.
fixed paths to test-data files
Some improvements in the ldpath-syntax definition