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 design of the tool/wobj base was to allow planning with either a pure
robot moveit package, or a custom one. In order to support that strategy, I
think what was missing is a frame_id for each of the base frames.

I would rather see the frame id's added to the adaptor, and an identity
frame used for the bases. That should help avoid future problems expanding
the usage.

The calls to actually get ik should always solve between two known frames.
Moveit::robotstate does some sort of automatic check and correction for
difference between the planning frames and ik solver frames