Also, copy the state between screens, so e.g. expanding a status in the
timeline and then opening that conversation already has that status
expanded.
This intentionally doesn't store the sensitive attachment visibility
state, since showing text when not necessary is less dangerous than for
images. (Possibly a preference for this in the future?)
Closes#55
Closes#49
This is a workaround for UIKit's built-in suggested context menu actions
not working as expected, and should be replaced with the system thing if
it becomes possible.