(Classic) System Ruleset ID

The pico engine has a system ruleset ID. The RID is system by default, but this can be configured. 

The engine uses this RID to write certain information about engine performance and metrics to application variables. These variables can be accessed by the ruleset that is registered with the system RID. 

Here are the application variables that are currently in use:

• rid_usage - stored the number of times a given RID has been accessed from the engine on the path ["requests",<rid>]