Apply master branch's commit (c27a840ca0140673194df37ccfb6e729e3137e29) manually.

 Fixed APIs to determine the max number of contact detected. Fixed bugs in FCLCollisionDetector. Now DART supports sphere-mesh collision via FCLCollisionDetector (you can switch the collision checker in ConstraintDynamics from FCLMeshCOllisionDetector to FCLCollisionDetector), though FCLCollisionDetector does not support other types of primitives.