Updating Pincher support based on suggestions from Michael Ferguson
   - Publisher is now same as original Arbotix, but publishes using jst_position rather than position
   - In Arbotix Driver, added new joint type: PrismaticDynamixelServo which inherits from DynamixelServo
     but updates jst_position in meters rather than radians
   - ParallelConvert now takes Joint name in initialization.  Uses /arbotix/joints namespace for params