Sawyer xacro, launch and yaml updates

[IanTheEngineer]

Resolves #1

• Adds sawyer_moveit.launch as the default entrypoint for launching
• Adds kinect_sensor and xtion_sensor yaml configs, launch args
• Adds rethink_electric_gripper srdf xacro files for Sawyer
• Adds sawyer srdf xacro files for self collision

[ShiweiWang]

Cool! looks good to me, if the FIXME is for something else in different patch , then Ship it :shipit: