Automate event handler disconnection

[coldfix]

When an object reaches its end of use, all its event handlers should be disconnected automatically. A couple of ideas how to achieve this

• global registry with all event handler connections
• when connecting a bound method, also keep track of event sources in the event sink object and remove these connections, when either object is invalidated
• use a different event mechanism. These at least sound interesting (will have to evaluate later):
  • functional reactive programming?
  • blinker?