Speed up loading of KDL and SRV kinematic plugins

This needs to be merged at the same time as https://github.com/ros-planning/moveit_core/pull/216

Improves the KDL and SRV kinematic plugins to load faster by bypassing loading and parsing the robot model.

Changes:
- Accept robot_model pointer
- Rename robot_state object
- Remove need for RDF loader
- Remove unused robot_state objects
- Cleanup formatting
Good point, I was not sure best practice for this. The problem is that we have to keep this function for the IKFast plugins in the wild that we cannot port (without asking users to regenerate them) but for KDL we no longer need this function. I could leave all the old URDF loading code in this plugin to allow this function to still load without having a RobotModel passed to it, but that seems like an overly-complex solution. As long as the new ``initialize()`` function is implemented (as it is in this plugin) this old version will never be called unless somewhere else in the API someone calls this deprecated version. If they do, they are using MoveIt! wrong this friendly error message will be displayed. Please explain how I could do this better.