Use `angular.extend` to update position in scope.
Use `angular.extend` to update position in scope.

This prevents dereferencing the original position object, which is undesirable
if there are other properties than `top`, `left`, `width` and `height` on the
position object.

For example if the position object is defined as follows:

    $scope.position = {
      top: 0,
      left: 0,
      width: 1,
      height: 1,
      name: "my first widget"
    }

Updating the widget would replace the original object, thus losing the `name`
property. Using `angular.extend` solves this by just copying all enumerable
properties from the object obtained through `Widget.prototype.getPosition` to
the original position object and leaves all other properties untouched.

patbuergin/angular-widget-grid,patbuergin/angular-widget-grid