Allow the Cacti administrator to subscribe to feeds/templates

[TheWitness]

Is your feature request related to a problem? Please describe.

Currently, Cacti attempts to insert all v9 and IPFIX flows into the flow tables. This could lead to some interesting results associated with flow types that simply make no sense to ingest. So, make the system smart enough to auto-detect compatible flow types, and leave the rest to be subscribed to separately.

Consider possibly adding these various templates to other table types to reduce the confusion associated with queries.

Describe the solution you'd like

Create a table that tracks the detected templates coming from devices. Allow users to pick the templates to subscribe to, once a template is subscribed to, start storing data, either to the current table, or a separate table.

Additional context

We need to see some templates coming from various devices before we pull the trigger on this feature.