Optical flow

[skhadem]

Initial optical flow branch, ready to be tested but not integrated yet, things that need to be done:

• Add custom message (use a darknet_ros one?)
• Add a list of classes to track, ignore bounding boxes that aren't in those classes
• Check for overlapping boxes to better filter out misdetections
• Better names for launch files (right now, just in orbit.launch)

[skhadem]

Word, I agree