1. Refactored show/hide/fade-in/fade-out out of InfoBubbleViewModel (into InfoBubbleView)
2. Removed InstantAppear/CollapseCommand (replaced by show/hide requests)
3. Introduced "InfoBubbleEventHandler" and "InfoBubbleEventArgs" for show/hide/fade-in/fade-out
Merge pull request #837 from Benglin/BubbleFading

Merge this pull request in so that Kah can continue working on more refactoring tasks.