Add collation to directory listings (#1823)

* 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.

graphql/schema/schema.graphql

@@ -7,7 +7,7 @@ type Query {
   """Find a scene by ID or Checksum"""
   findScene(id: ID, checksum: String): Scene
   findSceneByHash(input: SceneHashInput!): Scene
-  
+
   """A function which queries Scene objects"""
   findScenes(scene_filter: SceneFilterType, scene_ids: [Int!], filter: FindFilterType): FindScenesResultType!
 
@@ -25,7 +25,7 @@ type Query {
   findSceneMarkers(scene_marker_filter: SceneMarkerFilterType filter: FindFilterType): FindSceneMarkersResultType!
 
   findImage(id: ID, checksum: String): Image
-  
+
   """A function which queries Scene objects"""
   findImages(image_filter: ImageFilterType, image_ids: [Int!], filter: FindFilterType): FindImagesResultType!
 
@@ -127,7 +127,12 @@ type Query {
   """Returns the current, complete configuration"""
   configuration: ConfigResult!
   """Returns an array of paths for the given path"""
-  directory(path: String): Directory!
+  directory(
+    "The directory path to list"
+    path: String,
+    "Desired collation locale. Determines the order of the directory result. eg. 'en-US', 'pt-BR', ..."
+    locale: String = "en"
+  ): Directory!
 
   # System status
   systemStatus: SystemStatus!
@@ -149,7 +154,7 @@ type Query {
 
   # Version
   version: Version!
-  
+
   # LatestVersion
   latestversion: ShortVersion!
 }
@@ -275,7 +280,7 @@ type Mutation {
 
   """Run batch performer tag task. Returns the job ID."""
   stashBoxBatchPerformerTag(input: StashBoxBatchPerformerTagInput!): String!
-  
+
   """Enables DLNA for an optional duration. Has no effect if DLNA is enabled by default"""
   enableDLNA(input: EnableDLNAInput!): Boolean!
   """Disables DLNA for an optional duration. Has no effect if DLNA is disabled by default"""