Add the `SaltfileMixIn` to all CLI tool parsers.

is there any reason why `SaltfileMixIn` is only used in `SaltSSHOptionParser` currently?  I switch between a couple different projects that have separate salt configs and this would reduce a lot of `--config-dir .` repetition.

Far as I can tell, it should work with all the CLI tools, but I've a very limited environment to test this out, so please be careful with this.