fix(app-router): include error stack trace in logger

[baerrach]

closes aurelia/framework#926

[CLAassistant]

All committers have signed the CLA.

[baerrach]

I'm hacking this locally and am preferring this option instead

logger.error(result.output);

It doesn't double print the error message string and I still get the stack trace.

[baerrach]

Also, the output may or may not give object expansion toggles in your browser console. It appears to be browser specific.

This may only be a problem if you attach custom properties to your Errors and expect them to be inspectable in the console.

A workaround is to write your own implementation of the logger and use console.dir() if there's an error.