Android App: Use device back button to go back a pane, not leave the app

[SteveMicroNova]

Android devices have multiple buttons at the bottom of their screen at all time, one of which is the back button. Currently it takes users out of the app and is functionally equivalent to the home button; we should make it so that it just goes back a screen

Adding "good first issue" label because as far as I can tell it would just require adding an extra variable that contains the previously accessed url and routing that into the back button, correct me if I'm wrong