Fixed #4

- GameEntity now has a direction variable, representing the direction it last moved in, as a readable string.
- Movement can now infer a direction as well (such as 'the north'), which is used by Room.exited()/Room.entered()
- Movement broadcasts now use GameEntity.describeTo instead of toString
- DescType.ShortDesc removed (I've always considered it ambiguous)
- DescType.Name added in its stead.
- Tidied up syntax a bit in various places, to conform more with Java specs, and Scala standards.
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