Ability to import/export database

[kendallroth]

Request

Need to add the ability to import and export database to/from a device file. This will enable backing up important application state to share across app installs, etc.

This could use redux-persist if desired, or a most custom solution, as the state will be loaded into the app and then stored. However, using the library could decrease the amount of work required by standardizing shape, if it is possible.

Features

• Workflow for importing database (to file)
• Workflow for exporting database (from file)
• Ensure future Redux store migrations would be supported (via versioning)

[kendallroth]

Uncertain how possible this will be, as Expo cannot write to the external file system (ie. outside it's "sandbox"). Ideally the downloaded file would be stored in downloads, but the location could potentially be customized. However, no way exists to do this currently, other than a potential hack with using media library (unsupported for non-media files though).