Settings button toggles between Settings and Notifications

[hughlilly]

Closes #552. Not sure if this is the best way to go about what I’m trying to do, so I’d appreciate it if someone with much more experience than me would check over my suggestions. Thanks!

p.s. I think I stuffed up the commits. I wanted to make some other changes in 3d88d66 on another branch but they got included here. I hope I’ve reverted them properly.