Ad-hoc structural review (08/03)

Replacemnt package for pr2_gripper_action which adds additional functionality.

- fingersensor -> _sensor - slipgrip_controller -> pr2_gripper_sensor_controller - just call it controller and move actions into controller directory

- all action definitions should go in pr2_gripper_sensor_msgs

- add in seperate zero SERVICE zero_fingertip_sensors. return timestamp.

- force control action should return succeeded when the state of force control is succesfully entered and force achieved. - need to handle all states. such as not touching the tactile sensors

- change "place" to "gripper_sensor_event_detector"

- need to ensure that each action monitors controller state and handles changes appropriately.

- add in messages for state variables that define the different states

- higher level action to just grab stuff. smash state machine to string together

- all finger forces should be something like "fingertip_force".

- call motor effort something like "joint_effort" always

- slip servo should continue forver and give feedback

- add in "motors off" service and have all canceled actions fall back to this