Prepare using VehicleUpdate and PlayerMove instead of VehicleMove for
vehicle moving. This change isn't intended to change
anything/much on the surface.
* Implement native IEntityAccessPositionAndLook for 1.9_R1 and 1.9_R2.
* Alter method visibility and parameters.
* Common pre-conditions.
* Route contents of both VehicleUpdateEvent and PlayerMoveEvent through
a common related method (also named onVehicleUpdate).
* Remove RichLivingEntityLocation, to be able to simplify more.
* Refine interfaces for locations (IGet... ISet... vs, I... for both).
* Implement location related interfaces in some places, related changes.
* Override hashCode for some of the location related classes. Use that
for storing location hashes instead of Location.hashCode. Auxiliary
methods for hashCode in LocUtil.
* Add onIce to LocationData.
* Renaming player vs. vehicles (likely incomplete).
* Possibly other related/random changes.
Line count is high for this change, despite not so complex. Next step is
to change VehicleChecks to use past move tracking to estimate from where
a vehicle is moving (left not compiling). Due to the lack of teleport
events, and due to entity last location being mostly useless, we have no
choice but to hard-set-back on anything that looks strange.
