making the default method with no parameters supplied be a single type

[rmflight]

If you don't specify the method when calling ocv_keypoints, it currently fails because there are multiple inputs to the switch statement

# this generates an error, when it really shouldn't
mona <- ocv_read('https://jeroen.github.io/images/monalisa.jpg')
mona <- ocv_resize(mona, width = 320, height = 477)
pts <- ocv_keypoints(mona, method = "FAST")

[jwijffels]

Why not TYPE_9_16?

[rmflight]

I truly just picked one. I'll be honest, I'm just a user, I haven't followed the literature in this space, I think I just picked the first one in the list to use. If there is a better default, then it should be used instead. I'm fine with changing the default.