[kbnTopNav] break out controller, allow implementors to pass it in

The first iteration of `kbnTopNav` prevented the need to define a `configTemplate` and the `menuItems` in separate locations, but moved the external API to a `kbnTopNav` object that was exposed on the scope where `kbnTopNav` was rendered. This meant that in order to programmatically control the `kbnTopNav` other directives needed to share a scope with it, or inherit from its scope. Additionally, since the `kbnTopNav` object is potentially not available when other directives boot, all access to this object needed to be wrapped in a call to `$timeout`.

In order to prevent this, but keep the nice API of `kbnTopNav`, this change breaks the controller and it's API out of `kbnTopNav` and exposes it via a Private module. Now, implementors can instantiate the `KbnTopNavController` themselves and pass it into the `<kbn-top-nav>` directive via the config attribute. This allows implementors to store the topNav API wherever makes sense in their implementation.

When the config attribute is not already an instance of the `KbnTopNavController` the directive will create an instance out of the passed value, which means that no existing implementations need to change at all.

src/plugins/kibana/public/dashboard/index.js

@@ -2,7 +2,6 @@ import _ from 'lodash';
 import $ from 'jquery';
 import angular from 'angular';
 import chrome from 'ui/chrome';
-import 'ui/directives/kbn_top_nav';
 import 'ui/courier';
 import 'ui/config';
 import 'ui/notify';

src/ui/public/autoload/modules.js

@@ -1,6 +1,7 @@
 import 'angular';
 import 'ui/chrome';
 import 'ui/bind';
+import 'ui/kbn_top_nav';
 import 'ui/bound_to_config_obj';
 import 'ui/config';
 import 'ui/courier';

src/ui/public/chrome/directives/index.js

@@ -1,5 +1,3 @@
-import 'ui/directives/kbn_top_nav';
-
 import './app_switcher';
 import kbnChromeProv from './kbn_chrome';
 import kbnChromeNavControlsProv from './append_nav_controls';

src/ui/public/directives/__tests__/kbn_top_nav.js → src/ui/public/kbn_top_nav/__tests__/kbn_top_nav.js

@@ -3,12 +3,12 @@ import expect from 'expect.js';
 import { assign } from 'lodash';
 import $ from 'jquery';
 
+import '../';
 import navbarExtensionsRegistry from 'ui/registry/navbar_extensions';
 import Registry from 'ui/registry/_registry';
 import 'ui/navbar_extensions';
 
-describe('kbnTopNav Directive', function () {
-
+describe('kbnTopNav directive', function () {
   var build = function () {};
   let $testScope = null;
   let stubRegistry;