vyatta-cfg-vpn: add libnfnetlink-dev to build dependencies

Add libnfnetlink-dev to the list of build dependencies, required for
compiling src/cfgcti.

Bug #317 http://bugzilla.vyos.net/show_bug.cgi?id=317
vyatta-cfg-vpn: updated the debian package maintainer address
Merge pull request #9 from cyclops8456/helium

vyatta-cfg-vpn: add libnfnetlink-dev to build dependencies