Resolve 1160-backups-create-zip-files-zippping

Works, but a separate restoreFromFile method I couldn't easily build due to this.backupRestoreHelper.importAndToast(result) and the reader.readAsText(file) as well as the reader.readAsArrayBuffer(file)` methods.

A refactoring would be nice though, wasn't sure how to go about with it. ATM 31 lines.

Closes #1160 (closed)