ROS2 Port

[mikeferguson]

I've started working on this (https://github.com/mikeferguson/robot_controllers/tree/ros2) but figured I'd post a note here until we get a ros2 branch going on this repo.

Roadmap:

• [x] Port robot_controller_msgs
• [x] Port robot_controllers_interface
  • [x] Port ControllerLoader
  • [x] Port ControllerManager
  • [x] Port Handle and derived classes
  • [x] Move Controller, Handle(s), Manager, Loader classes into robot_controllers_interface namespace (this was arguably a bug in the original ROS1, which required all downstream controllers to depend on robot_controllers rather than robot_controllers_interface).
  • [x] Change ControllerManager to use service rather than action. The interface is a lot cleaner, and in ROS2 services can be asynchronous, so the deadlock fears in ROS1 are gone.
  • [x] Port python scripts
• [x] Port robot_controllers
  • [x] cartesian_pose
  • [x] cartesian_twist
  • [x] cartesian_wrench
  • [x] diff_drive_controller - planning to still tweak a few things still
  • [x] follow_joint_trajectory
  • [x] gravity_compensation
  • [x] parallel_gripper - ported, not yet fully tested
  • [x] pid
  • [x] point_head
  • [x] scaled_mimic
  • [x] trajectory tests
• [x] Add documentation to README that shows how to use updated interfaces

Bugs/Improvements to Look At:

• [x] Need to test cancellation of actions - probably need to change aborted() to cancelled() for them as well.
• Add a dynamic parameter interface to the PID class. Moved to #50

[mikeferguson]

migration docs are in: https://github.com/fetchrobotics/robot_controllers/pull/49

[mikeferguson]

PID dynamic parameters is now ticketed here: https://github.com/fetchrobotics/robot_controllers/issues/50

[mikeferguson]

parallel gripper now tested - we should now have feature parity with ROS1