Subgraph_t implementation. Fixed Bug at graph.h:1469
Merge branch 'graph-creation' of https://github.com/jmmut/common-libs into graph-creation
Finished and tested clustering coefficient functions.
Merge branch 'graph-creation' of https://github.com/j-coll/common-libs into graph-creation

Conflicts:
	containers/graph.c
	containers/test/graph_test.c