Add support for encrypted storage
Having encrypted device makes sense as it is pretty much possible to go to router and unplug usb stick.
My idea is to use cryptsetup with Luks. User would set its password and system would generate its own as well. This means that user password is not saved anywhere and system is using its own which is just plain stored on FS (keyfile).
Originally discussed in: https://gitlab.labs.nic.cz/turris/turris-os-packages/issues/208