Added UserDAO.getUsers() method and corresponding tests
Added UserService.getUsers method
Added UsersController getUsers method
Added list of ArticlePermission's as field in User entity
Added ArticlePermissionDAO.get (by userId only) method, changed ArticlePermissionDAO.get(userId, articleId), made corresponding changes in the test.
Added ArticlePemrmissionService.getArticlesPermissions method, modified .getArticlePermission
Added ArticlePermissionController