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.
I presume that this search is carried out by using the overloaded std::vector equals operator [here](http://www.cplusplus.com/reference/vector/vector/operators/)  in order to determine equality.  This may lead to multiple solutions that are effectively the same but still fail the overloaded equality comparison due to negligible differences in floating point precision.  An alternative would be to compare the difference against a small threshold in order to determine if they are close enough to be considered equal.