Better logging for SNMP traps with processing problems

We can do a better job of logging when Trapd receives a trap that gives our processing code indigestion (results in e.g. o.o.n.t.TrapQueueProcessor: Unexpected error processing trap: java.lang.ArrayIndexOutOfBoundsException: 6 in logs). Salvaging what information we can and logging it will help users track down the offending traps and their senders.

See also https://mynms.opennms.com/Ticket/Display.html?id=4801