- Ignore suffixed versions of build.sh (where I shove build logs) and
  of NookManager.img.
- Use `sudo` so non-root builds work sensibly.
- Add "uid=,gid=" VFAT mount options so don't have to `sudo` to write
  files.  (Doesn't affect the output image as the FS has no UIDs.)
- Move button labels up/down a little so long labels don't overlap.
- Separate the steps of zeroing empty space and making backup.
- Zeroing is unnecessary and takes ~10 minutes on a newish Nook.
- Keep button actions more static.  The "format" action already gives a
  sensible failure message when needed.
- Forgot the rest of previous commit (separate zeroing from making backup)!
- Contradict Jeff's note that 32-bit Linux is required to build.
- Use $IMAGE_FILE instead of NookManager.img, makes ad hoc testing easier
- Use `losetup -f` to get a usable loop device: some may be in use
- Use `parted --align=minimal` to allow tighter control over partition shape
- Explicitly start partition at 16KiB rather than relying on "cyl" alignment
- "An" SD card :)
- Report whether battery is Charging, Discharging, Not charging, Full.
- Operate with 20% charge as long as we're charging (externally powered).