Add new query types in ipaddr() filter

Three new query types have been added:

- 'host' returns only specific host addresses in CIDR format, no
  networks;
- 'net' returns only network addresses in CIDR format, no hosts;
- 'hostnet' / 'host/prefix' returns only host addresses with network
  prefixes in CIDR format (common way to express IPv6 hosts), if only
  host address or subnet is specified, it's skipped;
Merge pull request #40 from drybjed/update-ipaddr

Add new query types in ipaddr() filter