This is in preparation for being able to more finely control the NPC,
both from the specific NPC implementation and the PathNavigator (which
was renamed accordingly)
The PathNavigatorForKinematicBody node can take a KinematicBody as a
child and move it along its path. It doesn't strictly follow the path
though, but also avoids obstacles according to the Navigation (with its
Navmesh).
How the Navigation node is fetched will be changed using Groups later,
the current structure is temporary.
A PathTestWorld has been added for testing this behavior, as well as a
basic Meldewesen.
