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"/>.

Fixed face normals in collision meshes

Removed build dependency on roslaunch
Added run dependency on xacro
Updated package.xml to specify the supported variant

Added base link that corresponds to $ROBROOT coordinate system in the
KRC controllers.
Added comment that tool0 corresponds to the $FLANGE coordinate system.

Move joint origins to reflect the parameters used by KUKA in the KRC4
controller

Updated urdf and meshes s.t. the kinematics correspond to the kinematics
on the KRC controller.

Renamed joints to A1, A2, ...