[Development] Allow us to pull RelatedArticles from production APIs

useful for testing real world data

Suggested test config:
```
$wgRelatedArticlesUseCirrusSearchApiUrl = "https://en.wikipedia.org/w/api.php";
$wgRelatedArticlesUseCirrusSearch = true;
$wgRelatedArticlesDescriptionSource = 'wikidata';
```

This will allow us to enable on patchdemo with production content.

Change-Id: I73c0d73d3369f27ed2fd74b37ae71bfc12b6ee57

extension.json

@@ -61,6 +61,7 @@
 				{
 					"name": "data.json",
 					"config": {
+						"searchUrl": "RelatedArticlesUseCirrusSearchApiUrl",
 						"useCirrusSearch": "RelatedArticlesUseCirrusSearch",
 						"onlyUseCirrusSearch": "RelatedArticlesOnlyUseCirrusSearch",
 						"descriptionSource": "RelatedArticlesDescriptionSource"
@@ -122,6 +123,10 @@
 		]
 	},
 	"config": {
+		"RelatedArticlesUseCirrusSearchApiUrl": {
+			"description": "During development use a different API for sourcing related articles.",
+			"value": "/w/api.php"
+		},
 		"RelatedArticlesCardLimit": {
 			"description": "Maximum number of articles that should be shown in RelatedArticles widget. This limit is derived from limits in TextExtracts and PageImages extensions. Number should be between 1 and 20.",
 			"value": 3

resources/ext.relatedArticles.readMore.bootstrap/RelatedPagesGateway.js

@@ -63,6 +63,7 @@ RelatedPagesGateway.prototype.getForCurrentPage = function ( limit ) {
 	var parameters = {
 			action: 'query',
 			formatversion: 2,
+			origin: '*',
 			prop: 'pageimages',
 			piprop: 'thumbnail',
 			pithumbsize: 160 // FIXME: Revert to 80 once pithumbmode is implemented

resources/ext.relatedArticles.readMore.bootstrap/index.js

@@ -3,7 +3,11 @@
 	var data = require( './data.json' ),
 		RelatedPagesGateway = require( './RelatedPagesGateway.js' ),
 		relatedPages = new RelatedPagesGateway(
-			new mw.Api(),
+			new mw.Api( {
+				ajax: {
+					url: data.searchUrl
+				}
+			} ),
 			mw.config.get( 'wgPageName' ),
 			mw.config.get( 'wgRelatedArticles' ),
 			data.useCirrusSearch,