Display the loading spinner gif for all angular ajax requests

Remove the ajax-loader.gif which appeared only in unused styles.

app/common/loading-service.js

@@ -0,0 +1,10 @@
+/**
+* jamstash.loading Module
+*
+* Keeps the loading state across the app in order to display the spinner gif
+*/
+angular.module('jamstash.loading', [])
+
+.value('Loading', {
+    isLoading: false
+});