`ExtraneousLanguage` provides "extraneous" language functions independent
of MediaWiki required by Semantic MediaWiki and its registration system.

## JSON format

The location of the language files is determined by the [`$smwgExtraneousLanguageFileDir`](https://www.semantic-mediawiki.org/wiki/Help:$smwgExtraneousLanguageFileDir) setting.

### Field definitions

* `@...` fields leading with `@` are identified as comments fields
* `fallbackLanguage`defines a fallback language tag
* `dataTypeLabels`
* `dataTypeAliases`
* `propertyLabels`
* `propertyAliases`
* `namespaces`
* `namespaceAliases`
* `dateFormatsByPrecision` format used in connection with a specific precision and includes:
* `dateFormats` to a define a rule set of how to resolve preferred date formats for dates with 1, 2, and 3 components. It is defined as an array where the constants define the order of the interpretation.
* `months` twelve strings naming the months and short strings briefly naming the month
* `days` follows ISO-8601 numeric representation, starting with Monday together with the corresponding short name

### Example

<pre>
{
	"fallbackLanguage": false,
	"dataTypeLabels":{
		"_wpg": "Page"
	},
	"dataTypeAliases":{
		"Page": "_wpg"
	},
	"propertyLabels":{
		"_TYPE": "Has type"
	},
	"propertyAliases": {
		"Has type": "_TYPE"
	},
	"namespaces":{
		"SMW_NS_PROPERTY": "Property"
	},
	"namespaceAliases": {
		"Property": "SMW_NS_PROPERTY"
	},
	"dateFormatsByPrecision": {
		"SMW_PREC_YMDTZ": "H:i:s T, j F Y"
	},
	"dateFormats": [
		[
			"SMW_Y"
		]
	],
	"months": [
		[
			"January",
			"Jan"
		]
	]
	"days":[
		[
			"Monday",
			"Mon"
		]
	]
}
</pre>

### Date format constants

* `SMW_MDY` Month-Day-Year
* `SMW_DMY` Day-Month-Year
* `SMW_YMD` Year-Month-Day
* `SMW_YDM` Year-Day-Month
* `SMW_MY` Month-Year
* `SMW_YM` Year-Month
* `SMW_Y` Year
* `SMW_YEAR` an entered digit can be a year
* `SMW_DAY` an entered digit can be a day
* `SMW_MONTH` an entered digit can be a month
* `SMW_DAY_MONTH_YEAR` an entered digit can be a day, month or year
* `SMW_DAY_YEAR` an entered digit can be either a day or a year

### Precision constants

* `SMW_PREC_Y` Year
* `SMW_PREC_YMD` Year, Month, and Day
* `SMW_PREC_YMDT` Year, Month, Day, and Time
* `SMW_PREC_YMDTZ` Year, Month, Day, Time and Timezone

## Technical notes

* `ExtraneousLanguage` interface for the language functions
  * `LanguageContents` to provide the raw content from a corresponding language file
    * `JsonLanguageContentsFileReader` providing access to the contents of a `JSON` file
    * `LanguageFallbackFinder` is responsible for resolving a fallback language