Provide original error to system.error

We needed to log exceptions to the server. We managed to do this by using
```Javascript
    //>>excludeStart("build", true);
    system.debug(true);
    //>>excludeEnd("build");

    var systemErrorHandler = system.error;

    system.error = function (error, err) {
        // .... call to server ....
       
        systemErrorHandler(error, err);
    };
```

However, some messages are not as accurate as they could be, for example:
```
Failed to load routed module (viewmodels/budget-list). Details: Cannot call method 'initialize' of undefined
```

Now go ahead and find which variable is undefined - especially if you have many similar calls.

Proposed change gives access to inner error (which contains stack trace) in situation which gave us most errors. This way, in our error handler we can push full stack trace to server.