ipv4 lookup table rather than iterating match test

Previously, when we find ipv4 with given uid, we iterate ip and

generate uig and match test with given uid with generated uid.

Now we build uid-ip dictionary with ip adress range 16 when GroupVPN

starts. The overhead is trivial.
uid-iptable moved to UdpServer
Merge pull request #6 from kyuhojeong/gen_ipv4

ipv4 lookup table rather than iterating match test