Add support for a separation between a default validate/checkversion port and a runexploit port

[lobsterjerusalem]

In some cases you cannot fingerprint with the same service that the exploit is targeting. We need to add support that allows the following:

• Allows the dev to specify the common Validate/CheckVersion port, separately from the Exploit port if applicable
• If one is not provided, default it to the other, present port transparently
• If the ports are different, the Validate/CheckVersion steps should check the exploit service port to see if the service is available. This should require an additional callback to be defined.
• don't break the API on existing modules ( as usual )