Have a --noignore-file option

[blmatthews]

There are some builtin --ignore-files that I'd like to override (specifically not searching minified files), but there doesn't seem to be an easy way to do that (i.e. where I can just continue typing ack pattern). I'd like to suggest a --noignore-file option. I can see a couple of ways it could work:

1. If a --noignore-file option is given and there's a --ignore-file option in effect with the same right-hand side as the --noignore-file, drop the --ignore-file (and if there isn't a matching --ignore-file, maybe give a warning).
2. Collect the --noignore-files and if a file matches a --ignore-file, try it against the --noignore-files, and if it matches one of those, don't ignore it.

The first is probably easier to implement, but the second would also allow ignoring a large class of files but then overriding that for a subset of the class.

[n1vux]

since the email thread leading to this ticket has demonstrated there is a usecase / job-rôle where searching minified JavaScript (or equivalently minified CSS) would be the normal preference, not just a rare exception, this is a good thing to provide under our "every --thing has a --no[-]?thing" meta-rule, as --ignore-ack-defaults is a rather large mallet that removes too much.

Especially if we do something for #325 to provide characters of context around a match in those long lines ! e.g., syntactic sugar for long-lines workaround ack -o '.{0,20}string.{0,20}' might be used as ack --noignore-file --type=js --CC20 string (And this request supports that ticket and vice-versa.)