adding submenus functionality to the menu service

When having few modules like Articles, Blog, Services, etc... it's good to add the 'New Whatever' or other functionalities within a submenu structure.
updating calls to addMenuItem and addSubMenuItem

We can still create normal MenuItems without the 'dropdown' class.
Create dropdown on menuitems with submenus
little fix on removeSubMenuItem()
minor change on addMenuItem
minor fixes on client view
Reformat and bootstrappify the client home view.
Add a little info about the sample app
Changed all the indents to the spaces(tab size 4)
Typo in test message:
Merge branch 'pr/60' into 0.3.1
Merge branch 'pr/61' into 0.3.1
Merge branch 'pr/63' into 0.3.1

Conflicts:
	app/tests/user.server.model.test.js
	public/modules/articles/config/articles.client.config.js
	public/modules/core/controllers/home.client.controller.js
	public/modules/core/services/menus.client.service.js
Fixing Conflicts
Fixing Versions