Improved Friction via Muscle2P Changes, MLCP Solvers, accurate Tetraspine Model

This branch has four main features:

1) An updated version of Tetraspine that provides a better match to the hardware (most commits)

2) Support for Bullet 2.82's MLCP Solvers, defaulted to on: http://goo.gl/84N71q

3) Changing muscle2P to use applyImpulse instead of applyForce, leading to vastly improved friction performance. (see #83)

4) Removing the restriction that friction be <=1, since higher values appear to be useful for scaling. This was used widely within NTRT version 0.1, so should again be supported. However, further investigation is required for proper and accurate use.