Effort Controller Fixes 

* Critical bug: velocity controller init() does not get hardware_interface handle for joint
  * joint_ = robot->getHandle(joint_name);
* Added an optional target velocity for the effort_controller/joint_position_controller if you want to specify both a position and velocity target for use with the velocity_error in the PID class
  * JointPositionController::setCommand(double pos_command, double vel_command)
* Removed unknown code "friend class JointVelocityControllerNode" - no reference found anywhere in ROS codebase (hydro-desktop)
* Removed the need to used a scoped_ptr for control_toolbox::Pid after an upstream fix
* Cleaned up code & commenting

@adolfo-rt  @jbohren