[TASK] NL-3241 Change domain modeling

Classes/Domain/Model/Menu.php

Classes/Domain/Model/MenuInterface.php

Classes/Domain/Model/MenuItem.php

Classes/Domain/Model/MenuItemContent.php

Classes/Domain/Model/MenuItemLink.php

Classes/Domain/Model/MenuItemPage.php

Classes/Domain/Model/MenuItemSubmenu.php

Classes/Domain/Model/MenuTrait.php

Classes/Domain/Model/Page.php

Classes/Domain/Repository/MenuGroupRepository.php

Classes/Domain/Repository/MenuRepository.php

Classes/Hooks/ItemsProcFunc.php

Classes/ViewHelpers/Menu/Controller/RenderController.php

Classes/ViewHelpers/Menu/GetViewHelper.php

Classes/ViewHelpers/Menu/RenderViewHelper.php

Classes/ViewHelpers/Widget/Controller/ShowController.php

Configuration/Extbase/Persistence/Classes.php

Configuration/TCA/tx_nlmenubuilder_domain_model_menu.php

...iguration/TCA/tx_nlmenubuilder_domain_model_menugroup.php

Configuration/TCA/tx_nlmenubuilder_domain_model_menuitem.php