Support nested elements containing 'ui-sref'

Stopped event-propagation in the click-handler for uiSref-directive to support nested tags with `ui-sref`-attribute.

    <div ui-sref="root">
        Root-item description
        <div ui-sref="root.child">
            Child-detail
        </div>
    </div>

Clicking the "Child-details"-link will fire the `root.child`-sref as expected, but also the `root`-sref immediately after, **resulting in the `root`-state always being shown**.