Place MoveIt configurations in 'moveit' sub directory and clarify their status

[gavanderhoorn]

Related: ros-industrial/fanuc#305.

A README could then explain that MoveIt configurations were community contributed and may not work out-of-the-box for the specific configurations users have.

I would also suggest not to release MoveIt configurations -- as the readme would not be visible any more.

[gavanderhoorn]

Alternatively: create a separate motoman_moveit_configurations repository and store MoveIt configurations there.

This is not without precedent (see ros-planning/moveit_robots fi), and would allow git cloning just that repository in a workspace if/when users would like to use (one of) those MoveIt configurations.

The support packages and driver in this repository could then be released, and would not have to be built from source any more.

[gavanderhoorn]

@ted-miller @EricMarcil @marip8 @steviedale: opinions?