Improving KHH implementation (this one is one tough critter)
+ Time is now correctly parsed from the command line
+ Fixed bug where nodes in Seen were being deleted when restarting the search
+ Keyder, Haslum and Hoffman h^C algorithm properly implemented
+ Added methods to detect subsumed conjunctions
+ Fixed bug when looking up existing conjunctions
+ Added method to check if a set of fluents contains a mutex pair
+ Added method to evaluate a set of fluents
+ Added method to print a state
+ Added an example to show how to use h^C