allow wildcard filenames

this will allow to specify wildcard filenames, but as rsyslog cannot handle them as they are, we're going to expand the path to the actually matching files and making an entry for each of them.

given `/var/log/a.log` and `/var/log/b.log`

when our node is configured like this:

    "watch_files": {
      "/var/log/*.log": "foo"
    }

this will result in an entry for `a.log` and `b.log` both tagged as "foo"
Does this change the behavior now so that the watch files must exist at the time this recipe is run? I actually don't know if rsyslog supports that, but I believe we rely on being able to set this up before a service writes/creates the watched files.