Allow for a threshold on alerts for distributions

Currently the alerts that can be set-up for distributions will trigger if no files have been exchanged in a given period of time.

It would be extremely useful if we could add a threshold number of documents for the trigger.

This way if the threshold is set to "4" and less than 4 documents are processed in that period of time, then the alert will trigger.

If set to "0", then it will work exactly as it does right now.

See attached sample.

This will allow a more granular trigger, even allowing different threshold per period of time.

This function will be of great use for our business.