Add a way to play reverse mode

[Andriamanitra]

As much as I personally hate reverse mode there should still be some way to play them specifically. I'm unsure what the CLI for this should look like, maybe clash show --reverse which skips printing the statement (and maybe prints a warning if the current clash is not marked as reverse)?

[Andriamanitra]

#24 added logic for printing reverse mode clashes (used by default when it's the only enabled mode) but a CLI interface is still needed to access reverse mode in clashes that have other modes enabled.