Cleanup

• Fixed waiter_hide_on_render see #79.
• Added waiter_preloader shows the full page loading screen when the app is loaded and automatically removes it when all the UI is rendered: only runs once. #82
• Remove logging of shiny event, #83
• Fix stewart, broken due to removal of progress.js #81
• Added fadeout effect on waiter overlays, #53
• Improve waiter screen responsiveness.