made updateTransform() public so that models can be manually forced to re-clamp to terrain.  Particularly helpful when adding new height field layers to the earth.
(cherry picked from commit 4f16090f61e06d6dd464e68cffee5b5e8a714256)
Merge pull request #385 from poweroftwo/master

made updateTransform() public so that models can be manually forced to r...