Works on body drawing for bluff bodies with parameters.
incremental work.
Updates RigidBodyElements to call updateVisualShapes on model compile which should update the visual elements if a parameter has changed.  This is cleaner than updating in updateParams since it does not require a change in the arguments passed to and from that function.
Big change to the structure of the system.  Now the user must specify which wings have control surfaces at the wing level in the URDF.  This removes the control_surface tag and introduces the wing_with_control_surface tag.  Documentation still to be updated for the URDF.  Also changes RigidBodyManipulator to support parameters inside its frames, enabling paramters to work inside of elements like the origin of a wing.
Adds URDF documentation.

Also fixes a few bugs related to the parameters and updates tests.