targeter: make functional again

use common code from targeter_refined, and present
the same ROS api via /targeter/targeted
add some sample experiments

three examples of functionality
* a simple protocol for many repeated bouts
  of single laser stimulation
* a position dependent stimulation where flies
  are only targeted if they are in a certain part
  of the arena
* an example showing how to stimulate flies with
  two lasers concurrently