Improving Nameserver suffix handling

[MichaCo]

• Removing the filter during resolving namespaces from NRPT, the code can handle any suffix or namespace filter, doesn't have to start with .
• Adding Contains(string) to DnsString to, for example, find a namespace within a query string.
• Changing equals of NameServer to allow for multiple servers with the same IP/Port but different DnsSuffixes... (I might inverse that to a list of suffixes, but handling is actually nicer like this).

For more details, see #198 and the MiniDig change here which does an example of how to find nameservers using the new Contains etc...

[MichaCo]

splitting this into separated PRs