Enabled structure diagrams on the umpleonline website in both the righthand canvas and the generated diagram area.
Refactored the code generation javascript and the diagram update javascript.
Also moved error and warning messages to their own container.


git-svn-id: http://umple.googlecode.com/svn/trunk@4178 6ebf9d09-8eb1-0036-9d08-68c07d1b990a