Working on automaton

I'm actually quite proud of the clearness of Automaton.propose using maps and partial functions.
Better automatons

Partial executions don't have to know whether they're complete: the automaton already knows.
Simpler State operations.
The engine receives complete PEs and can directly choose one.
Initial work on delta valuations
EmptyValuation

For delta valuations initialization
Delta valuations

tests pass
Merge pull request #43 from Geogi/dev

Dev