http://refactoring.com/catalog/replaceTempWithQuery.html
Methode moved getCharge
http://refactoring.com/catalog/selfEncapsulateField.html
Abstract Klasse Price implementiert
http://refactoring.com/catalog/replaceConditionalWithPolymorphism.html and adding Price Classes
http://refactoring.com/catalog/replaceConditionalWithPolymorphism.html
small cleanups...