Need to split a types module out from notify-listen-beam

[madeline-os]

The HasNotification and HasChangeNotification classes need to be accessible to GHCJS so they should be decoupled from the backend-specific beam code.

[cgibbard]

Wait, why do they need to be accessible to the frontend? I can't see a reason.

[madeline-os]

They don't, but you want them to be in the common code so you don't have orphans when defining your schema.