Added Moveit adapter package

This implements the Descartes `RobotModel` interface for MoveIt.  The PR includes some parts of PR #13, but not all.  Method implementations for `TrajectoryPt` are not included.  However, these methods will simply be wrappers around RobotModel calls when required.
the setJointGroupPositions(..) [here](http://moveit.ros.org/doxygen/classmoveit_1_1core_1_1RobotState.html#aaf00ec8b048e7b23638858d2c1e0f56a) method should be used here in order to apply this to the planning group.