The enhancement of PredictorProvider's robustness

[okozelsk]

The configuration of predictors will now only be at the level of a group of neurons. Instead of a set of bool attributes and subsequent specification of parameters in separate child xml elements, each predictor will now have its own xml element. Multiple use of a predictor of the same type but with different parameter values will be allowed. The set of available predictors will be revised, unused predictors will be removed, used predictors will be generalized, and new predictors will be added.