Backup improvements & example

See merge request elixxir/elixxir-dapps-sdk-swift!110

This reverts commit 90d0e9a0.

This reverts commit 8578ae69.

Add MessengerStop function wrapper

See merge request elixxir/elixxir-dapps-sdk-swift!109

Remove facts from BackupParams

See merge request elixxir/elixxir-dapps-sdk-swift!108

Restore facts from UD

Messenger - backup

See merge request elixxir/elixxir-dapps-sdk-swift!107

- When first data arrive, ignore it and add params to the backup
- When following data arrive (that included params), handle it