* Replaced the log-output backed command wrapper with a simpler solution (LP: #269044). * Now logging to ~/.usb-creator.log instead of just stdout. * Moved the persistence code from the backend to scripts/install.py and wired up the persistence scale in the frontend. * The backend now reports the task description in addition to the progress value. * A failure dialog is now shown when scripts/install.py exits non-zero (LP: #269035). * Mount the target device at install time if it has not already been mounted (LP: #269032).