Add support for IP ranges

[debuggest3]

Currently, you can only ban single IP addresses using !banip. I know that it's technically possible to ban ranges, so add support for that.

[xhoogland]

Do we actually still want this. Yes, it is indeed technically possible, but I haven't seen any complains/requests/questions so far that we really need this?

The impact of a rangeban is of course quite high and I don't know about the possibility of having exceptions for this.

[TotalEpicFailure]

Commenting here to show support for this. Banning serials is more limiting than range bans are (in that there are more possible ranges than there are serials).