new method return_graph
insert arraylist<String>, return listenablegraph
Some testgraphs are now displayable over GUI
true for Graph 3-5,7,8.
Nullpointer exception at 1 and 6, illegal argument error at 2.
Merge branch 'master' of https://github.com/alexmantel/GKA

Conflicts:
	bin/controller/FileLoaderController.class
	bin/model_impl/GraphHandlerImpl.class
	src/controller/FileLoaderController.java
	src/model_impl/GraphHandlerImpl.java