Added Recast/Detour.

Also added initial POC code for integrating it in Ember.
Use recast for steering.
Visualize the path.
Polish steering.
Made visualization optional.
Initial work on dynamic awareness.
Interleave navigation with rendering.
Use a marker to cancel event handlers.
Clean up at deletion.
Handle entity awareness better.
Define awareness using a rotbox.
Load tiles in the middle of the area first.

To optimize it a bit we'll make sure that the tiles that touch upon the
direct path from the current position to the destination are loaded
first. In most cases this will be enough to find a path.
Cleanup and docs.
Move to destination to final waypoint.
Cancel steering if we move ourselves.
Added method for quickly blitting heights.
Use faster method of getting heights.
Integrate Recast log with Ember log.
Clarify API.
When stopped we'll retain small awareness.

The reasoning here is that it's probable that we want to move within the
nearest vicinity.