Apparently there are phones where accessing Dolphin's app-specific
directory isn't just annoyingly hard but actually impossible.
To give users of those phones at least some kind of way to manage
their data (even if it's a lot less convenient than if we were
allowed to let the user open the app-specific directory in a
file manager), I'm adding a way to export the directory to a
zip file and then import it back.

Apparently some phones (at least some from Samsung) don't expose the
system file manager in the system settings despite it being the
only on-device file manager that can open app-specific directories...

To make it clearer for users where Dolphin is storing user data,
now that there's more than one possible place.