Option to turn off a world from showing in bottom right corner

[ray73864]

Add an option to stop a world from showing in the bottom right corner even if it has new activity.

The general idea behind this is you might have a development world opened all the time, lots of development type messages might be showing on it, but you don't want to see if it has new activity.

The option should only hide it from the bottom right corner, it should still maintain having the 'New Activity' display in the world output.