Update PR2 Beta URDF based on arm drawings (ros ticket #3565)

[ahendrix]

Function has provided mechanical drawings for the PR2 beta arm. URDF should be updated accordingly.

trac data:

• Owner: vpradeep
• Reporter: vpradeep
• Reported at: Thu Jan 14 11:40:44 2010
• URL: https://code.ros.org/trac/wg-ros-pkg/ticket/3565

[ahendrix]

[vpradeep] Done. r29183