Add --snmp-max-repetitions option that influences the get_table() call

There is an issue with get_table() and how it iterates over multiple OIDs as it is doing the SNMP walk.  This can lead to too much data being received as part of get_table(), or no data at all being received.  From the client perspective, the requests may timeout, even with very large timeout values.  If this occurs, setting the "-maxrepetitions" setting to get_table() to "1" usually makes it work properly.  

This patch implements a new CLI option "--snmp-max-repetitions".  It defines the number of OIDs that will be iterated over after the first bulk request.  If set to 1, it essentially falls back to a get_next_request() and repeats that until finding an OID that is not in the initial request.  The option is passed into the get_table() call as "-maxrepetitions".