Changed the way articles are listed, the way list is filled with new group of
new articles, and not refreshed with new ones.
Also, exceptions handling is improven.
	modified:   Gruntfile.js
	renamed:    services/ExceptionHandler.js -> config/exceptions.js
	modified:   controllers/LoginController.js
	modified:   controllers/MainController.js
	modified:   directives/CheckPresence.js
	modified:   public/app.js
	new file:   services/ExceptionsService.js
	modified:   services/FeedsService.js
	modified:   services/FoldersService.js
	modified:   services/ItemsService.js
	modified:   services/UserService.js
	modified:   templates/main.html