TinkerGraph can supportPersistence(), should we allow it.

We could support this:

// configuration file
graph.tinkergraph.graphLocation=/tmp/mygraph.xml
graph.tinkergraph.graphFormat=graphml

Then on GraphFactory.open(configuration) a TinkerGraph will be created and it will automagically graph.io(graphml()).readGraph(/tmp/mygraph.xml).

Finally, and most importantly, on TinkerGraph.close(), graph.io(graphml()).writeGraph(/tmp/mygraph.xml).

spmallette Had initial aprehensions about this idea (but he can't remember what they were). I will assign it to him so he can express his concerns.