Document the registered process in the .app file

This helps systools detect registered name clashes

Author: Vagabond

src/lager.app.src

@@ -9,7 +9,7 @@
                   kernel,
                   stdlib
                  ]},
-  {registered, []},
+  {registered, [lager_sup, lager_event, lager_crash_log, lager_handler_watcher_sup]},
   {mod, {lager_app, []}},
   {env, [
             %% What handlers to install with what arguments