Feature/extension manager (#689)

* getting the extension gallery from a static file and enabling the extension manager

extensionsGallery.json

@@ -0,0 +1,13 @@
+{
+"results": [{
+	"extensions": [
+	],
+	"resultMetadata": [{
+		"metadataType": "ResultCount",
+		"metadataItems": [{
+			"name": "TotalCount",
+			"count": 0
+		}]
+	}]
+}]
+}