Convert ulsPurpose from a data attribute to an languagefilter option

src/jquery.uls.languagefilter.js

@@ -236,7 +236,7 @@
 				this.$element.trigger(
 					'noresults.uls',
 					query,
-					this.$element.parents( '.uls-menu' ).data( 'uls-purpose' )
+					this.options.ulsPurpose
 				);
 				return;
 			}
@@ -342,6 +342,10 @@
 		lcd: undefined,
 		// URL to which we append query parameter with the query value
 		searchAPI: undefined,
+		// What is this ULS used for.
+		// Should be set for distinguishing between different instances of ULS
+		// in the same application.
+		ulsPurpose: '',
 		// Object of language tags to language names
 		languages: [],
 		// Callback function when language is selected