Output filering in the client

[Th4nat0s]

I could be convenient to be able to filter out the results directly with the client.

For Exemple;

usage: pdns [-h] --query 111.123.123.123 --since 3m
To output directly only results last seen in the last 3 months.

[Rafiot]

We can't do it server-side (see #42), adding it client side is possible but moderately useful as we still need to get the complete dataset from the server first.