Updated install to emmc script

[jravetch]

Opening a new PR to get the emmc install script added, based on comments #25

[aw]

@jravetch hey! ✨

[pfeerick]

The revised script is looking good. I think there is an issue with line 56 (suffix) though, as when I added xenial-containers as a supported image type it failed completely (couldn't find a matching image) until I changed it to arm64 instead of arm*. It otherwise worked fine OOTB.

[jravetch]

Thanks @pfeerick for catching that. I've updated the script to reflect arm64.

[pfeerick]

No problem @jravetch ;) Can I also suggest (unless the advise has changed although it appears to still be valid from the latest release notes), that jessie-openmediavault be checked for before setting the suffix, so that an armhf suffix can be used if jessie-openmediavault is the image specified (maybe also add stretch-openmediavault and do the same for it since it's there for testing also now?). And that xenial-containers be added as an install option (as well as added to the help message). I'll give it another run through in a couple and days and prompt ayufan to review/include it...