adds orocos_kdl dependency and linking rules (fixes #8)

With these changes I'm able again to compile and run the robot_state_publisher again.

I'm a bit confused about the completely missing orocos_kdl dependency though. I wonder how it ever was possible to compile this package at all?! The library and both executables all depend on KDL directly.

So, since it compiled before, I'm not 100% sure my proposed changes are correct/the best way. So far this was the approach I took for all my packages involving KDL. If there is a better solution, please let me know.