Annex B features now listed as n/a in non-browsers

Since Annex B features are only required for browsers, non-browser
implementors now show a gray "n/a" instead of "No" when they're not
supported.

This also updates the feature-sorter code to account for non-applicable
features.
Changed listing from "n/a" to grayed "Yes"/"No"

Now, both the presence or absence of an optional feature is drawn gray,
but still shows "Yes" or "No" anyway. Thus, the information regarding
implementation status is retained, but is highly de-emphasised.

Also, gray result squares now have an informative tooltip.
Shift annex B features to the bottom

To save on maintenance (and to produce a cleaner diff), this is done
programmatically.
Merge pull request #182 from webbedspace/annexB

List annex B features as optional on non-browsers