import keys - test several keys in one prv backup (clipboard or file)

[DenBond7]

Need to test import backups which generated using the approach from #252

Settings ==> Keys ==> Import ==> Load from file (Load from clipboard)

[DenBond7]

Currently, we support import only one key per action

[DenBond7]

Also, such a situation with a variant when a user setups the app and don't have any backups. Then he can import his key if he has it.

[DenBond7]

@tomholub Do I need to do that for the current milestone(0.6.4)?

[tomholub]

I think so. If we support exporting such keys, importing should also be possible on the same app