Improve Apriltags Docstrings and Defaults

[TheTripleV]

docstrings / API

.detect - Input image has to be grayscale
.getCorner* - Specify that idx 0 is the bottom left corner OR change the functions to getTopLeftCorner etc.

Config Defaults

minClusterPixels should be increased from 5. I think to at least 200 (0.2% of a 240p frame).
criticalAngle should be increased from 10 degrees to at least 45 degrees.

^ Or higher for both.

The defaults should be too strict and allow teams to loosen the detector, not too loose and force teams to get rid of noise.