Find way to improve matrix updates

[gkjohnson]

We know exactly when matrices need to update because the angles get set so possibly we can improve the matrix update performance.

[gkjohnson]

Plan:

• Add a 'jointNeedsUpdate' or jointNeedsUpdate field to joints indicating they need an update (or just use existing matrixWorldNeedsUpdate flag)
• Override the URDFRobot updateMatrixWorld function to iterate over all joints and update their local matrix as well as their childrens world matrices
• Add an optimizeMatrixUpdate field to URDFRobot that defaults to false that enables or disables this behavior

matrixAutoUpdate could also be disabled by default on the non-joint nodes but it wouldn't be as optimal was the above strategy.