Make more camera presets available

[jamesremuscat]

(Deferred from HD upgrade work)

The new cameras support up to 50 presets, and they persist when the power is cut.

It might be nice to be able to access more of these presets from the touchscreen - perhaps in "banks" which could be allocated to specific operators.

[rjmunro]

Do we even need presets on camera? Why not just remember the location of the camera and command it to go to that location from the touch screen?

[jamesremuscat]

Position, zoom, focus, white balance, aperture, shutter speed, gain, EV compensation... that's a lot to keep track of ourselves, when the camera already has built-in functionality to do so.

Someone did ask about this already: jamesremuscat/avx#29. I see using more of the camera's preset memory as a relatively quick win.