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 current branch hydro-devel shows that the wobj_base_ is checked against the last element of the link names array "back()" .  According to the discussion above, should it be compared against the robot base instead or the first element in the link names array "front()"?