[Dev] New block event dispatchEnumType

[Bryan Stearns]

Hi John,
 
Donn made ToolbarItems act more like regular widgets, which allowed me to
push the stamping code down from the Markup Bar to a common base class that
the individual stamping ToolbarItems inherit from. This means the
ToolbarItems themselves want to receive the ButtonPressed event.
 
I didn't see an appropriate BlockEvent.dispatchEnumType to use for this:
SendToBlock is too specific, none of the Broadcast* ones fit, and the
existing ~BubbleUps started at blocks other than the event sender. So, I
added SelfBubbleUp - the new case in View.dispatchEvent() looks like:
 
    elif dispatchEnum == 'SelfBubbleUp':
        block = notification.data['sender']
        bubbleUpCallMethod (block, methodName, notification)
 
Does this look reasonable?
 
...Bryan