Add variables into the Trigger system

System variables including $SERVERVERSION, $USERNAME, $2DAYSAGO, and others are only available in Session Group Filters.  It would be valuable to include the ability to use these variables in the Trigger system.

An example where the trigger would be helpful is here:

Event.EventType = 'Connected' AND Session.SessionType = 'Access' AND Session.CustomProperty1 LIKE 'XYZ Company%' AND Session.GuestClientVersion <> '23.4.4.8560'

This trigger can be used to send an e-mail when an out-of-date access agent from a specific company connects to the control server.  Unfortunately, this trigger needs to be manually updated every time a new Guest Client Version is released.

The other variables would also improve the filter quality.