Reduces the visibility of all fields to private and create setters/getters
when necessary. Exceptions are fields with GuiSync as these need to be
public.
Reduces the visibility of internal methods to private/protected/default when possible.
The AE2 has in the contract that the item field in an IAEItemDefinition can be null due to the fact, if a special item is deactivated. This needs to be checked.
The base code was enhanced through Javadoc and split in responsibilities
