add a logout page

allows destroying user session with a minimum number of loaded dependenciesi.
Can be Used for SSO forwards (logout).

Co-authored-by: Nicolas PARQUET <nparquet@linagora.com>

www/logout/main.js

@@ -0,0 +1,5 @@
+define(['/bower_components/localforage/dist/localforage.min.js'], function (localForage) {
+    localForage.clear();
+    sessionStorage.clear();
+    localStorage.clear();
+});