Display’s a non-dismissable copy of the beta/media message in the footer after dismissing the standard message

- messages broadcast a `’message:hidden:messageId` event when dismissed
- media & beta messages are shown in the footer once dismissed
- media & beta messages reordered slightly, to avoid unnecessary string concatenation 
i wasn’t sure if we did - isn’t the messaging system able to take messages from anywhere? so far only these two exist, but it seems conceivable there could be messages that can be dismissed and then don’t want to be pinned to the footer. depends how likely that is i guess