Add support for igmp and multicast

Add support for igmp and multicast

Multicast can be enabled through configuration or through command line
- Through configuration
  Add multicast=mcast_address (e.g. multicast=01:00:5e:01:02:03) in the port
  section
- Through command line
  run enable multicast port_id mcast_address (e.g. enable multicast 1 01:00:5e:01:02:03)

IGMP join message is sent unsollicited through command line:
  join igmp core_id task_id ip (e.g. join igmp 1 0 224.1.1.3)

To enable swap answering IGMP Query (w/ IGMP Join)
- Through configuration
  Add igmp ipv4=ip_address within the core/task section
- Through command line
  join igmp core_id task_id ip (e.g. join igmp 1 0 224.1.1.3)
  (this will 1st initiate an unsollicated join, then answer any subsequent query)

UDP/TCP packets received on a multicast address (224.0.0.0 => 239.255.255.255) are discarded

To stop sending responses to IGMP query:
  leave igmp core_id task_id

Change-Id: I3808ccabf3b38b5a1e10e1b044db63aa05bcd7b5
Signed-off-by: Xavier Simonart <xavier.simonart@intel.com>