[feature] import / export config

[jrpie]

(suggested by Sarp Küçük)

Please describe the problem to be solved

When moving to a new device, manually restoring the old settings is tedious.

Describe the solution you would suggest

There should be an option to export the settings and import them on the new device

[jrpie]

Before implementing this, the storage format for preferences should be updated. Especially the way actions are serialized needs to be updated (this is also a problem for impleenting things like #45 )

[jrpie]

depends on #81