add simple excetion wrappers
add the new exceptions to loadFromGson (still unhandled exceptions)
 'handle' simple exceptions in Client
add DrachenExceptions
add gson adapter for DrachenExceptions
add exceptions to register
add exceptions to login
comment login and register
add exceptions to logout
add CredentialException to gson adapter
add exception to loadQuestPrototypes
extracted ParameterException
add ParameterException to gson adapter
add exceptions to locationForId
extract ExceptionDisplayFunc, and add Exceptions to loadLocationForest
add Exception to startQuest
add Exceptions to abortQuest
add ObjectRestrictionException
add Exceptions to questFinish
comment methods