Perform movement prediction of the avatar entity

Perform movement prediction of the avatar entity without having to wait for server responses.

We currently don't move the avatar until the server has responded to a movement request. This makes for a bad gameplay experience, especially with high ping.
It would provide for a much nicer experience if we updated the movements of the avatar locally before we get any response from the server.
We can currently pretty well predict the position of the avatar as long as it doesn't collide with anything. As soon as that happens the experience becomes very jarring though. So before we implement this fully we need to have proper client side collision detection.