clsNetwork: Resolve and validate networking addresses

This class can be used to resolve and validate networking addresses. It can:

- Resolve an IP address to obtain the corresponding host name and vice-versa
- Check whether an host accepts a connection to a given port
- Calculate the subnet masks / subnet IPs
- Compare and validate masks
- Validate an IP address to check if it belongs to a subnet with a given mask
- Validate IP and MAC addresses
- Check for IP overlaps