Structured passkeys, internally and on the options and popup pages.
Fix regression: reinstate confirmation dialog for restoreToDefaults
Retain excludedUrls setting, so testers can revert to previous versions.
Structured exclusion rules: Fix typos and minor issues.
Structured exclusion rules: Simplify isEnabledForUrl.
Structured passkeys; changes following code review; major rewrite of options.
Add some style advice

These represent common feedback given on PRs
Add some guidelines for PRs
Clearer reset-to-defaults confirmation message.
Merge pull request #1154 from smblott-github/passkeys-structured

Structured exclusion rules internally, and on the popup and options pages.