Quote strings in bash populated YAML files.

Quoting is hard.  When writing strings into YAML files, wrap them in single quotes.  Also escape any embedded single quotes in those strings via a double signle quote ('').
Sure, the `sed` way works for me. Unfortunately shell has lots of these corner cases and we'll never really going to get to the end of this.

Satnam and I were discussing rewriting a lot of what is currently shell in Go and I think that's really the way forward. Keep shell for what it was intended, which is mostly <20 lines scripts which do not actually do anything as fancy as this...

In any case, let me know when you have the `sed` version and I'll merge it in.

Cheers,
Filipe