Commented NAT stuff out of 30-gateway.conf.  Not that it matters, because...

Transplanted the "Set up the mesh gateway stuff" into the working dhcpcd.enter-hook script.

Signed-off-by: The Doctor <drwho@virtadpt.net>
Transplanted the "Tear down the gateway stuff" code into dhcpcd.exit-hook.

Fixed a bug in dhcpcd.enter-hook where I called a bad variable.

Signed-off-by: The Doctor <drwho@virtadpt.net>
Merge branch 'master' of https://github.com/Byzantium/Byzantium