Got rid of double Refresh when deleting Entity

When an entity was being removed from EntityWorld,
EntityManager.Remove(entity) caused Refresh(entity) two times: once in
Remove, once in RemoveComponentsOfEntity.
Now it:
1) cleares TypeBits;
2) calls Refresh (causes every System's.OnChange)
3) nulls Components in Component containers
Merge pull request #60 from Maximusya/master

Got rid of double Refresh when deleting Entity