1.4.0 - Add Diffie-Helman Based SNMP Data Collection

# Feature Request

## Is your feature request related to a problem? Please describe

Some SNMP devices will only support querying them via snmp if they support Diffie-Helman key exchange.  Add this feature to Cacti.

## Describe the solution you'd like

Add this functionality to Cacti and spine.

## Describe alternatives you've considered

Not using it.