Make graph blocks more mathematical ('set y' -> 'y =', 'get x' -> 'x') and add 'x' block to workspace on load.
Review URL: https://codereview.appspot.com/9556043

git-svn-id: http://blockly.googlecode.com/svn/trunk@919 c400ca83-b69d-9dd7-9705-49c6b8615e23