Initial commit of KUKA KR120 support package

Added support for the KUKA KR120 R2500 PRO manipulator
Meshes are based on the Unigraphics files found at http://www.kuka-robotics.com/res/sps/8ba89f50-3ccd-4361-9b9a-60bdd0662ac6_KR120_R2500_pro.prt.zip
Note that the rotation directions of the KUKA manipulators are different than e.g. the ABB manipulator. For joint 1 this is implemented using <axis xyz="0 0 -1"/>.
I understand. But the top of the mesh is not always the correct location of the joint. For Fanucs fi, based on D-H data or the datasheet, `joint_1` is most of the times *outside* `link_1`. It can be several tens of cm away from the mesh. The mesh origin is then also somewhere outside of the mesh.

As I said, this is only important if we want to be able to correlate transforms to links in the urdf with the real-world robot.