Add success and log messages attributes to sensor

[chriss158]

Hi Thomas,

I have added the following attributes to the sensor:

• LAST_BACKUP_SUCCESSFUL -> Display in a simple boolean value if the last backup was successful
• LAST_LOG_MESSAGES -> Show the last log messages starting with the last "Backup running ...".

This way it's easier to check if something failed and see the error messages immediately.
For example, I have a node-red flow that sends me a notification after the backup is done. If something failed, the log message is attached to the notification.

Some notes on the implementation:

• I changed the path of the .samba_backup.sensor file to the config folder instead of the backup folder. The backup folder is used by HA and I think this folder should not be used by addon for custom files.
• Known issue: The last log message "Backup finished" is not in the LAST_LOG_MESSAGES attribute. I think the output via bashio::logs.info and calling ha addon logs self is too close together. Even with a sleep of 20 seconds I cannot get it to show up in LAST_LOG_MESSAGES.

Thanks again for reviewing 👍