Added new package for velocity-based controllers: velocity_controllers
Adding source and include files for joint_position and joint_velocity controllers.  These are still copies of the effort_controllers version of the same.  velocity_controllers_plugins.xml has the proper namespace inside to add velocity_controllers rather than effort_controllers
Changed namespace and function names from effort to velocity, changed command_interface from EffortJointInterface to VelocityJointInterface
Set up velocity controller for a pass-though without pid loop
Changed velocity controller to have a better debug message, changed the namespace variables, added a gitignore file.
modified the velocity controller to broadcast state messages, and load limits from the urdf file.