Phone app to configure options

[ysamlan]

Have checkboxes for blackout mode (no UI in the watch app) and a checkbox to disable the instructions+toasts.

This is a feature request from a user; sounds reasonable, but we should make sure it doesn't slow down app restart when trying to re-lock after the phone is turned back on (maybe by defaulting to a black screen without blocking on the disk read, then accessing the settings in the background after activity start and showing the UI only if needed).