Appcache Updates Should be Handled better

[jloutsenhizer]

Right now appcache updates obscure the entire screen and force a refresh when they complete. This is jarring to the user:

1. It shouldn't be a required refresh
2. Because it shouldn't be required refresh the user shouldn't be prevented from using the site while the resources are saved
3. If another tab/window navigates to the website and there's an appcache update, all instances receive the update events

Ideally there should be a little bar at the bottom that pops up to give you info about the progress and give you a button to click when you are ready to load the new version. When this button is clicked it should do all the necessary things to make sure the current game (if any) has all its data saved