REFACTOR: Repulsion's intersection find method is now static

There was no particular reason to have that be an instance method, since
we can just pass the vehicle as a parameter instead of just its position.

I'll likely move it to an independent tool class in the future, since I
may have use for it on other behaviors.
Updating changelog
BUGFIX: SteerForPursuit was drawing the debug force incorrectly
SteerForTether is now a post-processing behavior

This makes more sense, since the tether itself should be a correction
force on the vehicle's desired velocity, not a force in and of itself.
SteerForEvasion is now a post-processing behavior

This helps overlay it with other behaviors in a more natural fashion,
since we can steer the vehicle while still keeping away from a target.
SteerForPursuit now can optionally use the full approach force

Previously we were using the default value for GetSeekVector, which
subtracts the velocity from the approach vector.  The default is now to
apply the full force.