Snapshot metadata

This isnt for merging yet, just WIP,

Bit of a slow start, but figured while I am still finding my way around the codebase i'll raise this so ppl can peek at the progress more conveniently and give me feedback as i go.
> I'm assuming here that the list of strings is a list of lines to write to the file,

You probably know now but you can use `utf8` instead of `linesUtf8`.