App Already Bootstrapped with this Element '{0}'
Occurs when calling angular.bootstrap on an element that has already been bootstrapped.
This usually happens when you accidentally use both ng-app and angular.bootstrap to bootstrap an
application.
<html>
...
  <body ng-app="myApp">
    <script>
      angular.bootstrap(document.body, ['myApp']);
    </script>
  </body>
</html>
Note that for bootstrapping purposes, the <html> element is the same as document, so the following
will also throw an error.
<html>
...
<script>
  angular.bootstrap(document, ['myApp']);
</script>
</html>
You can also get this error if you accidentally load AngularJS itself more than once.
<html ng-app>
  <head>
    <script src="angular.js"></script>
    ...
  </head>
  <body>
    ...
    <script src="angular.js"></script>
  </body>
</html>