Filtering can be done by given selection network.

[iercan]

This patch allow filter connections by given networks when getting dump.

i.e.

ct = pynetfilter_conntrack.Conntrack()
ft = pynetfilter_conntrack.Filter()
ft.select_networks = [IPy.IP('127.0.0.1')]
    for item in ct.dump_table(filter=ft)[0]:
        item.destroy()