Implement exposure equations and matching for Aperture menu
Implement exposure equations and matching for Aperture menu

Also: More evidence I am in a continual half-daze

- Need to define shutter value as double in `aperture` as otherwise both
  arguments will be integers and I'm guessing it'd not going to work out
  well. Plus... need to use `fraction_to_double` anyway to feed the
  value in.
- Had done the "substring" thing wrong in `strncpy` and was one decimal
  place off in getting the paerture value. I.e. would have got "1."
  instead of "1.4" from "f/1.4"
- Like the fool I am, in the loop and the copy and paste I'd done, I'd
  not changed from `aperture_array[0]` to `aperture_array[n]`

atomicules/exposurses