implement the occasional respawning of certain enemies and randomness to enemies

[Zaechus]

Currently, killed enemies remain dead and new ones never take their place. Enemies should return to a room after a time. Spawn time should be based on elapsed moves, and randomness might be a good idea.

[Zaechus]

Some enemies are now created with certain random stats. More will be randomized later.

[Zaechus]

It will probably be useful for this and a lot of other potential features to keep track of the number of moves (like Zork), be able to output it, and only increment after an Active command.

[Zaechus]

Added move counting to the game