fst: support fstinfo
I wanted to know where OpenFST stands on is-deterministic when there are spontaneous transitions. The answer is: Open FST does not care about them wrt determinism: the `one` label is treated like any other label. This is something I was considering for Vcsn too... But I'm uneasy with this, so I think I will rather introduce a new property P, and define deterministic as having P and no spontaneous transitions. See also #196. * python/vcsn/automaton.py (fstinfo): New. * tests/python/efsm.py: Check.