added a vision module

"mavproxy_rasp_pi.py" is a modified version of mavproxy.py that removes
user input, logging, and changes the APM datastream

"mavproxy_vision.py" is a mavproxy module that enables autonomous
tracking

"vision module documentation.txt" should be reviewed before trying to
use the vision module

the files in the "vision utils" folder are for training a classifier,
designing color filters, and debugging the tracking algorithm. see
"vision module documentation.txt" for more info.