Updated SDN-IP to use Ip4Address and Ip4Prefix instead of IpAddress and
IpPrefix, because so far we haven't implemented IPv6.
Also, some of the BGP-related attributes (e.g., BGP Speaker ID)
are IPv4 by definition.

The following components are updated:
 * BGP implementation
 * Router component and relevant state (e.g., RouteEntry)

Other components (e.g., configuration) will continue to use
the more generic IpAddress and IpPrefix.

Change-Id: I1936ca9871fd5a9709cb4f2c2850d78ebc1472c4
14 files changed