Merge pull request #966 from lakkatv/lakka

Use setting_data_get_string_representation + fix a bug
(Menu) Refactor menu_action_ok
(Menu) Add MENU_FILE_DIRECTORY type to switch
(Menu) Refactor common code in disp/rgui | rmenu | rmenu_xui
(Menu) Create two new types - MENU_FILE_SHADER and MENU_FILE_SHADER_PRESET
(Lakka) Fix subitems allocation