Added steering centre members to VehicleData.

steeringReturn is the main control for the amount of return in
the steering. Setting it to 0 (the default) disables steering return
completely.

steeringReturnSpeedScale is a multiplier on the amount of effect that
the vehicle's velocity has on its steering return.

powerSteering can be set to eliminate the effect of steering return on
user input. Without this flag set, the user will have a harder time
steering, because the wheels try to return as they steer. If this flag
is set, steering return will not be applied while the user is actually
steering, only when they release.
Added steering return to Vehicle.

It happens in Vehicle::updateMove so it can apply to all vehicle
subclasses. It is applied to both x and y steering.
Fixed stream read/write mismatch bug.

It was causing Vehicles to roll forwards with a constant velocity when
stationary, and ignore move->y.
Add getMaxDamage() method.  This will be needed for the forthcoming HealthTextHud GuiControl.
GuiHealthTextHud.  A C++ GuiControl that replaces the scripted numerical health hud.
Removed the scripted numerical health hud in the Full Template and added the new GuiHealthTextHud control to the playGui.
Script changes for the Full PhysX Template to remove the scripted numerical health hud, replacing it with the c++ GuiHealthTextHud GuiControl.
Send back RayInfo distance with ContainerRayCast

Added an 8th word to ContainerRayCast's return, which is the distance.
Doc changes for RayInfo distance

Doc changes for the containerRayCast DefineEngineFunction to include the
distance.
BitVector don't have copy-constructor/operator=
Added compilation information to README.md
Fix for Issue #88 for River Editor Snapping
Merge pull request #89 from DavidWyand-GG/issue88-RiverEditorSnapping

Fix for Issue #88 for River Editor Snapping
Updated readme with PhysX 2.8.4.6 information.
Fix for Issue #90 for Camera orbit object bug
Merge pull request #93 from DavidWyand-GG/issue90-CameraOrbitObjectMove

Fix for Issue #90 for Camera orbit object bug
Fix for Issue #94 for Cubemap render bug
Merge pull request #95 from DavidWyand-GG/issue94-CubemapRenderBug

Fix for Issue #94 for Cubemap render bug
Fix for Issue #96 for DAE updating crash
Merge pull request #97 from DavidWyand-GG/issue96-PhysXCrashOnObjectUpdate

Fix for Issue #96 for DAE updating crash