Feature suggestion: add support for USB storage of images / use USB instead of MicroSD card

[greiginsydney]

The MicroSD card resident in the Pi has a theoretical maximum number of read/write cycles in it. I've never had one fail, but it's regularly suggested to use external (SSD) storage as an alternative.

This might also add some speed improvements, although obviously with an increased power consumption requirement, and the need to introduce a USB hub into the signal flow between Pi & camera (given the Pi Zero W and Zero 2 W only have one workable USB port).

[wj7106]

I am very much looking forward to the release of this feature version, and if possible, I also look forward to supporting the Sony a7r2,a7r3 system