Use SNMP getbulk for OID retrieval

The basic idea is, the poller process could use SNMP getbulks for OID retrievals. Polling items individually can cost a lot more resources than doing them in batches, especially using over SNMP. Instead of being every OID a separate request, getbulks could be used.

The way I could image this, is teaching the polling scheduler to take look at the queue for the given host, and if more SNMP items are awaiting, they could be fetched using one or more getbulks, instead of individually. This would make polling somewhat easier and faster.