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
There's a lot of redundant information here - we are able to get base and tip name from robot model and group name (this is true of the earlier initialize function too). I would change this initialize function to not include base and tip name or robot description.