updates from 6.832 class prep / demos

adds a few plotting utilities
adds gradients to barycentric code
adds the quadrotor wrl model (so people will be able to run the 3D quadrotor demo w/o an lcm visualizer)
adds simple function approximator demo

According to http://www.mathworks.com/help/matlab/ref/inline.html:
inline will be removed in a future release. Use Anonymous Functions instead.