* matrix-backup-borg: added option for unencrypted repo access

* matrix-backup-borg: fixed requiring password for unencrypted repos; changed variable name

* matrix-backup-borg: add unknown_unencrypted_repo_access_is_ok to config.yaml.j2

* matrix-backup-borg: cleanup comments

* matrix-backup-borg: add documentation regarding unencrypted repos

* matrix-backup-borg: add readability and ease of use to code

* matrix-backup-borg: fix wording in defaults/main.yml comment

* matrix-backup-borg: add quotes to docs

* Indicate the variable to use

Co-authored-by: Slavi Pantaleev <slavi@devture.com>