added basic implementation for iteration 10
added foreign keys to entities

some experiments on persistence problems with Highscore
prototype implementation of generic repository and service
cleaned up service

removed non generic methods and usages from service, context and repository
improved UI layout for highscores
changed layout for questioning view

added hsk1.csv
added workaround to avoid exceeding the maximum message size of WCF or IIS
changed font for characters
fixed failed unit test
added unit test