katana_description: fixes for groovy

ivcon and convex_decomposition are now on the global PATH, not in the
package dirs any more
update URDF to be compatible with Gazebo 1.5

In the ros-groovy-simulator-gazebo update to 1.7.12, Gazebo was switched
over to 1.5, which breaks compatibility with old-style URDFs. This
commit updates to the new version.
Increased gripper opening duration to 8.0 to avoid timeout
Merged commit 27be36d0f from Steffen P.s groovy branch
Merge commit '27be36d0f' into fuerte
Merge commit 992671e0c from Steffen