Update core-controllers

* Authenticated_Controller now extends ICF_Controller
* Public_Controller checks for permission on 'public'
Update module acl to deny deleting resources 'public' and 'admin'
Add folder structure for module navigation
Add migrations for module navigation
Add models for module navigation
Add models for module navigation
Merge branch 'feature/navigation' of github.com:ignitedcode/iCF into feature/navigation

Conflicts:
	icf/modules/navigation/models/navigation_menu_m.php
Add first management scripts for admin/navigation
Fix bug in model acl/acl_role_m::_before_create_slug
Add lang line eng/icf.message.delete.not_confirmed
Add column 'acl_resource' to table navigation_items
Add first version of module navigation

* Can manage menus
* Can manage items (per menu)
Update ICF_Model: Add ICF_Model::id_by_slug
Update core/{ICF,Public}_Controller: Move 'user'-var to ICF_Controller
Update module navigation: Allows building menu from slug on layouts
Add navigation-template for 'admin-menu' of theme 'huraga'
Add some exceptions to .gitignore
Add missing 401-html to icf/cache/{acl,mailer,navigation}
Update view huraga/navigation/admin-menu
Update module navigation: Caching and flushing works