Add interactive mode to Banshee

This is just a prototype; it fails for maps larger than the terminal size, for
example :).
Make the interactive interface more robust

Center the view on the banshee, unless we are at the edge of the map. I'm a bit
surprised that resizing works, too :).
Refactor the interactive interface
Add a help
Improve the help window
Add "long steps" with pgup/pgdown keys
Add autoplay mode

The autoplay works correctly only from runhaskell; see
http://stackoverflow.com/questions/15304317/ . `getEvent` doesn't wait
when the code is compiled.
Add some huge maps

The maps suggest that there might be room for improvement, because the
large map causes a stack overflow with the default stack size.

Also found an incredible bug -- the program fails when no path is found!!
Fix a non-exhaustive case bug

Function `wallStep` didn't count with mazes without paths :).
Add more huge castles

Another problem found -- program fails on array index error when a scout runs
out of the castle.
Check scout's position in sliceCastle
Add some castles generated by a cellular automat