This commit adds support for OpticalFlow to MinnowBoardMax trying to
leave the OpticalFlow implementation as generic as it already is.
We had to add some format conversion and software crop to the cameras that
do not have this features.
Onboard Optical flow needs to have access to the ahrs to get
correct gyro values.
Therefore the constructor takes the ahrs as a param like it is done
for other classes that need to have access to these datas
Lucas De Marchi
mirkix
Ricardo de Almeida Gonzaga
Julien BERAUD