Make the pad types displayed on the front page configurable

customize.dist/application_config.js

@@ -0,0 +1,10 @@
+define(function() {
+    var config = {};
+
+    /* Select the buttons displayed on the main page to create new collaborative sessions
+     * Existing types : pad, code, poll, slide
+     */
+    config.availablePadTypes = ['pad', 'code', 'poll'];
+
+    return config;
+});