* Add collation to directory listings. Closes#1806
Introduce a new `locale` arg to the `Query.directory` field. Set "en"
as the default for the field for backward compatibility. Use the given
locale, sending it through a language matcher, and use `x/text` as the
collation engine for the matched language.
Augment the file `ListDirs` call to optionally take a Collator. If the
Collator is given, sort file listings according to the collators rules.
While here, document the GraphQL schema a bit more.
Add matchers by looking at the current front-end locales, and make sure
each of these occur in the matcher list.
* Language matcher touchups
* Avoid having `en-US` twice.
* Introduce `en-AU`.
* Pass IgnoreCase and Numeric collation
Allow the collator to be configured with options. Pass the options
IgnoreCase and Numeric to the collator.
