Flip anchor points so the context menus don't go offscreen.

git-svn-id: http://blockly.googlecode.com/svn/trunk@1658 c400ca83-b69d-9dd7-9705-49c6b8615e23
Switch from SVG context menu to HTML dropdown menus.

git-svn-id: http://blockly.googlecode.com/svn/trunk@1659 c400ca83-b69d-9dd7-9705-49c6b8615e23