VLAN support with vdev devices + few other changes

VLAN support with vdev devices + few other changes

- vdev devices now support VLAN.
- kernel tap device can be configured with a netmask (/24 was
  always used in previous version).
- when sending a (fake) packet to the kernel, this packet will now
  not be routed by the kernel (i.e. it will leave through the
  interface configured by PROX). This might change in the futture
  when PROX supports multiple VLANs per port. But today it prevents
  ARP being sent on management interfaces.
- Log error in case kernel unable to send packet.
- Added support for comments (';') in lua sections.
- Prevent duplication of local_ipv4 - should now be configured in port section
  local_ipv4 in core section still supported

Change-Id: I8f9a40fe6ad6f3013ff91b58b44627c7f34081e6
Signed-off-by: Xavier Simonart <xavier.simonart@intel.com>