borg handler should support additional options passed to borg commandline

It would be great to be able to pass options to the borg handler, which would need to be passed to each invocation of borg.

I'm thinking to --remote-path for instance (unless that one desserved its own settings option, of course).

Thus, instead of invoking "borg [command] it could be something like "borg [command] $additional_args"

Hope this makes sense