Store & create graph for peer-as

The purpose of theses patches is the get the same stats as AS-Stats, but for peer.
Instead of looking for the real source & destination, we will get focused on the neighbor who sent us the data, and the neighbor you will receive the data.
These data are not 100% accurate (because it is based on as-path), but still usefull to graph usage if you have a paid peering over an IX (with the same snmp port, vlan etc), and if you want monitor the bandwidth used