Editing the styleguide HTML does not trigger watchers

[edwinm]

In the generated styleguide, it's possible to edit the HTML (with CodeMirror) and see the results when properties and content are changed.

Changing the properties this way does not trigger the watchers. Besides watchers, also beforeUpdate, updated and prop handlers are not called.

This can lead to undesirable side effects.

Solution: make sure the right handlers are called when a property is changed.