Display facts for aliases in *BSD

* interfaces.rb - aliases on *BSD are iterated over up to their actual count - slightly modified Michelle Sullivan's version
* util/ip.rb - added get_alias_no method to return alias count; method get_interface_value modified by Michelle Sullivan to allow obtaining values for specific aliases

Originated here:
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=190796

It's not "my piece", but I suppose the reason would be that traditionally aliases in FreeBSD are (and have to be) configured in /etc/rc.conf beginning with 0. So alias0 makes sense and corresponds to something that HAS to exist if you're using aliases. It's only an "associative" as ifconfig doesn't actually list "alias0, alias1, alias2", but for anyone comparing facter output with what's configured via /etc/rc.conf it makes sense.