feature: support dynamic subitems

[zoladkow]

With this PR we should be able to provide an array of submenu options dynamically, like so:

children: $q(function (resolve) {
    resolve(
        function ($itemScope) {
            return service.prepareSubItems($itemScope, jumpOptions);
        }
    );
})

[josetaira]

Thank you for your contribution, @zoladkow!