changed subsetgraph: subsets can now be contained in the graph
added ContainsSubset method to subsetsuperset graph
invert and List<Integer> constructor to ColumnCombinationBitset
added superset graph, test and fixture
updated/added javadocs, small code format changes
updated test javadocs
removed blank lines
changed invert() to be directly on the OpenBitset
renamed SubSupersetGraph to SubsetGraph
changed invert(int) method according to the feedback on github
updated javadocs for contains...
Merge pull request #162 from Jens-Hildebrandt/master

SubSupersetGraph extension