Implemented collision resolution heuristics.

The whole system needs quite a few changes to be at last proudly called 'an algorithm'. But it works, for now!
Events now react only to specified actor.

Map's 'defaultActor' property, little cleanup and actors' management.
Changed actor types to lowercase.
Added 'door', 'bridge', 'spawn' actors and 'trap' event.

Yeah!
Debug mode now depends on arg[1] being 'debug'.