Every learning method now inherits from the abstract class LearningMethod, instead from the interface ILearningMethod.

ENH + FIX: Fixed output problems of MSE evaluation and the data-set is not de-normalized anymore, when evaluating an error, thus the error can be evaluated multiple times (e.g. using different networks).

FIX: Fixed non-normalizing eval() method in ErrorFunctions + rewritten ErrorFunction classes to prevent duplication of code.

ADD: added proggress debug output for particle swarm optimization