[TASK] Extbase: Revised and cleaned up autoloader. Autoloader is now registered insid...

[TASK] Extbase: Revised and cleaned up autoloader. Autoloader is now registered inside the Dispatcher (at construction time). The autoloader of Extbase is only invoked for extension classes. The core autoloader takes care of the Extbase and Fluid classes (auto-generated ext_autoload.php file). Medium performance improvement.
[~TASK] Extbase (Utility): Improved the conversion CamelCase to under_scored. Implemented Ulility methods. Small performance improvement.
[BUGFIX] Extbase (Persistence): Fixed issue if MM_match_fields was not set. Checks for array now. Reported by Joerg Schoppet. Resolves #4072.
[TASK] Extbase (Persistence): Cleaned-up the Persistence Backend. Deleted unused methods deleteRelatedObjects() and deleteRelationInRelationTable(). They will be re-implemented later on.
[+FEATURE] Extbase (Utility): Adapted the createAutoloadRegistryForExtension() feature from exdeveval.