FILEMAN-44: Add a checkbox on top of others to check them all

I must admit I wasn't aware of the ``indeterminate`` property of the checkbox element. It's very good that you have used it but the way you set its value is not quite the Angular way. I would rather add a [custom directive](http://stackoverflow.com/questions/22143417/angularjs-custom-directive-for-a-ng-indeterminate-attribute-on-checkboxes).