AI related bug fixes and improvements.

Removed references to AIObjective and aiAvoidThis which are not used.
Made minor improvements to the spawning system in the aiPlayer.cs file.
Got rid of AIManager related comments.
Added a flag that sets the transform of spawned objects.
Added a console method to get an AIPlayer's move speed.
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.
Changed function name to fit standards.
Merge branch 'development' of https://github.com/TwistedJenius/Torque3D into TwistedJenius-development
Merge branch 'aiplayer-fixes' of https://github.com/eightyeight/Torque3D into eightyeight-aiplayer-fixes
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.
Fix for Issue #62 for Large decal disappears
Merge pull request #63 from DavidWyand-GG/issue62-LargeDecalsDisappear

Fix for Issue #62 for Large decal disappears
Fix for Issue #64 for GuiTabBookCtrl rendering
Merge pull request #65 from DavidWyand-GG/issue64-GuiTabBookCtrlRendering

Fix for Issue #64 for GuiTabBookCtrl rendering
Rename AiPlayer::produce() to AiPlayer::spawnAtLocation()

... does what it says.
Fix for Issue #66 for Skinned mesh crash
Merge pull request #68 from DavidWyand-GG/issue66-SkinnedMeshCrash

Fix for Issue #66 for Skinned mesh crash