Update restic to version 0.13.1 and add option to check data integrity

[lojutaan]

This pull request updates restic version to 0.13.1 and adds option to run restic check to verify data integrity. Data integrity check is optional and by default doesn't do anything.

• A new check.sh script is added to the image. check.sh is modified version of backup.sh. Instead of running restic backup it will run restic check. This script will have it's own hooks and log files
• A new environment variable CHECK_CRON is created. Same as BACKUP_CRON but for check.sh. If left unset data will not be checked. Default is unset
• A new environment variable RESTIC_DATA_SUBSET is created. Value is passed to --read-data-subset when repository check is run. If left unset only the structure of the repository is verified. Default is unset
• Added example docker-compose.yml to README

[leadZERO]

Wondering if you could update this to the latest release? Thanks for doing this work!

[niondir]

Sorry, I did merge the update to 0.14.0 first. Can you please update the pull request to also include the latest restic version? I will then merge the PR.