Support digital alarm blocks

[cnlklink]

Right now only ACNET analog alarms are support. Extend support to digital alarms.

[beauremus]

This is new functionality for the parameter page. This is currently handled in a separate application.
Just documenting for context.

[rneswold]

More documentation/brainstorming:

A digital alarm block gets downloaded to the front-end. It gets routed by the SSDN associated with it in the database.

• In all my drivers, the digital alarm has the same SSDN and NODE as the basic control property.
• It is possible that the digital alarm has a different SSDN.
• It is also possible that the digital alarm has a different NODE.

The parameter page would have to set up a (very slow) periodic read of the digital alarm block (to adapt when new settings are downloaded to it) as well as a periodic read of the device that is truly reading the status for it.

The param page would get the status and do the bit-twiddling to see if it's in alarm.

I think part of the GraphQL get_device_info reply should have a field that holds the device that returns the status used by the digital alarm.