Fix up fs.watch functionality

Not ready for commit yet.   Doc improvements to follow in a subsequent commit.
Correct, they behave identically in JS. Reasons to prefer single quotes off the top of my head:
1. less visual clutter, especially when there's multiples them
2. they don't behave differently, so only using doubles for JSON makes their use there stand out
3. quite often JS contains quoted HTML, and HTML uses double quotes, so there's a lot less escaping of quote marks to contend with.