added traj control via objects to move both arms at once. unfortunately, each execution of end-effector path seems to be blocking (so arm movements are sequential---left arm moves to goal, then the right arm moves to goal).  I know i've had both arms execute a plan at once before---i did test this under some configuration---so i need to see how to make that again.  i might have to wrap the moveit_interface code in a thread to make things concurrent.