Deletes a class from the storage.
[OperationContract]
[FaultContract(typeof(BioIDWebServiceFault)]
bool DeleteClass(BiometricClassID classId);
Returns true when the given classId existed and has been deleted, false otherwise.
All entries associated with the given classId are deleted from the storage. When this class does not exist,
false is returned, otherwise true, indicating, that the class has been deleted.
This deletion cannot be undone!