Final public API for predictor classes

[Zruty0]

1. All predictor classes should be named SoAndSoModelParameters (like KMeansModelParameters, LinearBinaryModelParameters etc.

2. Strive to remove unnecessary interfaces from the public API: thinks like IPredictor, IPredictorProducing<float> etc. should not be public.

3. Review the public surface of ModelParameters to enable ONLY parameter introspection. For example:

• KMeans should only expose centroid coordinates.
• Linear should only expose weights/biases.

4. If possible, try to add public constructors. For example:

• Make it possible to create KMeansModelParameters from centroid coordinates
• Make it possible to create LinearBinaryModelParameters from weights and biases

[glebuk]

@sfilipi ensure that it's all done and close.