Represents the Singleton object, which is the hub os all Cartella objects, managers and events.

Its main purpose is to maintain a list of SiteManager instances, also relay all events issue from the SiteManager instances.

CartellaGlobalManager is designed to hold a given number of SiteManager instances and keep them around. There will be a expiration time set on each SiteManager. If within the expiration time threshold, no Methods or Properties calls happened on the SiteManager instance at all, the SiteManager instance will be automatically dropped from the pool and erased.

This system allows system not need to create a SiteManager instance everytime, also in the same time, not use too much memory to store every unsed SiteManager instances.