Resume and Suspend

have two new functionalities:

• suspend: This is like temporarily disabling callbacks for a script. This is good because if an entity goes bizarre after executing some callback, it should be easy to disable a callback. 
• resume: re-enable a callback which has been suspended. The callback must be register for resume.

suspend and resume can happen for event callbacks that have been registered.

We currently have a "system.reboot" which clear the complete state of the script. This is like getting a new scratchpad..