Feature: use native types for BGP related fields in flow (RD, comms, ecomms, AS path, etc...)

[rodonile]

In the bgp-pkt create we already have types for BGP related fields such as RD, comms, ecomms, which we could use in the Field enum similarly as done for tcpControlBits.

Non exhaustive list:

90	mplsVpnRouteDistinguisher			    octetArray
483	bgpCommunity					        unsigned32
484	bgpSourceCommunityList			        basicList	
485	bgpDestinationCommunityList		        basicList	
486	bgpExtendedCommunity			        octetArray	
487	bgpSourceExtendedCommunityList		    basicList	
488	bgpDestinationExtendedCommunityList	    basicList	
489	bgpLargeCommunity					    octetArray
490	bgpSourceLargeCommunityList			    basicList	
491	bgpDestinationLargeCommunityList		basicList	
511	bgpSourceAsPathList					    basicList
512	bgpDestinationAsPathList				basicList