libct: Add libnl as git submodule

Ubuntu 14.04 contains old version of libnl, which can't work with
veth devices.

Signed-off-by: Andrey Vagin <avagin@openvz.org>
net: use libnl

This patch replaces our netlink code on libnl calls.
libnl: return handle on net device

It will be used to configure it.
namespaces: export net_ns
net: add function to apply configuration on net device
net: add ability to set mac address
net: remove parts of rpc