Upgrade App's dialogs to originate from SVG elements as well as HTML elements.  Make the OneTopBlock dialog appear from the topmost block.  Tweak the timing of the dialog animation.  Add work-around for the missing Australian flag in Puzzle (Chrome bug).  Fix URL parameter decoder to recognize + as an alias for a space.

R=spertus@google.com

Review URL: https://codereview.appspot.com/12901043

git-svn-id: http://blockly.googlecode.com/svn/trunk@1216 c400ca83-b69d-9dd7-9705-49c6b8615e23