Wrap `console.log` in a try/catch

Add the `safe_console.js` module which wraps `console.log` in a
`try {...} catch() {...}` because IE8 doesn't supply `console.log` when
the developer console isn't open.
Add `excanvas` to jqplot dependencies (if IE version < 9)

Internet Explorer 8 and earlier doesn't support canvas. Thankfully the
"explorercanvas" module can supply it for us.

https://code.google.com/p/explorercanvas/
Show empty values in piechart-widget