Multiple instance branch merge back to trunk

I've merged the multiple plone instance branch back into the trunk. I hope 
this won't have broken too much on other branches.

I had to make one change to the way the KupuEditor class works: I've 
removed the call to grab the focus in the initialize method. This means 
that if you were depending on Kupu to grab the focus when it loaded it 
won't any more, so you may want to add a focusDocument call to your 
initialisation code.

The problem is that with more than once instance of Kupu on a page you 
definitely don't want both to grab it, even if it is just Kupu and a few 
other web controls on a form there is no reason to assume that Kupu should 
get focus first.

IE in particular delays the action of setting focus which results in two 
Kupu instances each trying to grab focus from each other. This leads to an 
almost unkillable IE crash since nothing else in the system gets focus long 
enough to hit the confirmation button on the kill dialog.

TODO: I need to write up the api changes and in particular how to 
initialise Kupu so as to be compatible with multiple instances. Also should 
I make the html multiple instance code use the new code since that way we 
can simplify and remove old code?

Also TODO: change the class constructor code to separate instances 
properly. I suspect this also means a big refactor to attach all methods to 
the prototype instead of assigning directly to this otherwise there are 
issues overloading methods in derived classes (specifically the zoom tool 
uses the prototype form to overload methods, but if you then call the base 
class constructor its instance methods will take precedence).