Borgmatic

* 199: Add note to documentation about using spaces instead of tabs for indentation, as YAML does
not allow tabs.
* 203: Fix compatibility with ruamel.yaml 0.16.x.
* If a "prefix" option in borgmatic's configuration has an empty value (blank or ""), then disable
default prefix.

* Only log to syslog when run from a non-interactive console (e.g. a cron job).
* Remove unicode byte order mark from syslog output so it doesn't show up as a literal in rsyslog
output. See discussion on 197.

* 193: Pass through several "borg list" and "borg info" flags like --short, --format, --sort-by,
--first, --last, etc. via borgmatic command-line flags.
* Add borgmatic info --repository and --archive command-line flags to display info for individual
repositories or archives.
* Support for Borg --noatime, --noctime, and --nobirthtime flags via corresponding options in
borgmatic configuration location section.

* 198: Fix for Borg create error output not showing up at borgmatic verbosity level zero.

* 195: Switch to command-line actions as more traditional sub-commands, e.g. "borgmatic create",
"borgmatic prune", etc. However, the classic dashed options like "--create" still work!

* 191: Disable console color via "color" option in borgmatic configuration output section.