Changes:
- moved all menu elements definitions from SkinMinerva into
a separate Definitions.php file
- moved menu building from SkinMinerva into includes/menu/Main
folder
- introduced Builder pattern for easy menu building
Minerva/Menu/Main/Director takes an Minerva/Menu/Main/IBuilder
and builds the menu. The IBuilders use definitions from
Minerva/Menu/Definitions file, so all definitions can be shared
across different menus
- used ServiceWiring file to register MainMenu Director as Service
- left class_alias for old MenuBuilder as some extensions still use it
- The hooks system have to stay like that as some extensions
are using it (BlueSpiceMultiUpload and GrowthExperiments).
- introduced AdvancedMenu builder for the AMC mode
Bug: T216152
Change-Id: I210c3f1fa36bbd2f9108d728b12cbb21ee210354
