Add under review passthru controllers from upstream ros_controllers

[egordon]

While waiting on a review of ros-controls/ros_controllers#569

This creates the following controllers:

rewd_controllers/JointGroupEffortController
rewd_controllers/JointGroupVelocityController
rewd_controllers/JointGroupPositionController

With only the joint_names argument.

Allows for either a subscriber float array connection-less interface (via the command topic) or a JointGroupCommandAction (from pr_control_msgs, see personalrobotics/pr_control_msgs#3)

[amalnanavati]

To protect against users calling init twice, perhaps clear joints_ before adding the joints to it?

(And/or add an is_initialized bool that is set to true at the end of this function and is checked at the beginning of this function?)

[egordon]

Good idea! Added

[amalnanavati]

With the exception of the change in init (which imo should have been in the original ROS code as well), this looks good.

FYI, I effectively reviewed the upstream commit to ros-controllers as opposed to this one, to better capture the diff.

[amalnanavati]

LGTM

[egordon]

Closing. Superseded by personalrobotics/pr_ros_controllers#26