Use object for settings
Use object for settings

Previous settings are ignored. Current settings are stored as base64
encoded JSON in 'settings' table in 'settings' key.

Also upgrade DB on wallet decryption.

jiri-novotny/arizen,woky/arizen,ZencashOfficial/arizen,ZencashOfficial/arizen,jiri-novotny/arizen,woky/arizen,woky/arizen,ZencashOfficial/arizen