Add SNMP SET (write) Capability

[cwolf908]

Currently, the plugin only supports SNMP GET functionality which is great and all we need for monitoring capabilities. However, SNMP SET or "write" functionality would allow Elastic to execute functions against devices including configuration backups. Having conrfiguration backups stored in elasticsearch would be fantastic for CM, but would also enable us to execute detection rules against configurations for known indicators of compromise, miconfigurations, etc.