Prototype adapter: removeEvent doesn't remove all events

[TorsteinHonsi]

Steps to reproduce:

1. Open http://jsfiddle.net/highcharts/8yhz3/
2. Click "Destroy"
3. Drag middle bar to resize the demo iframe
4. Errors are thrown because the resize event handler is not properly removed.

To fix it, set up a unit test on adding and removing events on window, DOM objects as well as Highcharts object. Test this with element parameter, element + event name and element + event name + handler.

[eolsson]

Events on 'window' where mistaken for custom events and the wrong stopObserving method was used.