Base class for all CUSTOMTOOLS extensions.

Inheritant must implement Hook(CTInterface) and UnHook(CTInterface). Inheritant should have minimal or no constructor at all. For (un)initialization purposes implementations of InitNotify and UnInitNotify can be overridden.

To provide various funtionalities for core product, inheritant should implement GetInterface(ctExtensionInterface) which must return valid object in every state of this extension. However, functions of the interfaces are not called unless the status is at least ctExtensionStatusInitialized.