rename the GPC modular

@karlnapf 
this is a big patch.
I just test it at one shot.
I will send a PR for the notebook tomorrow since switching different branch is annoying when some error occurs in this PR 
thanks for this point.
In fact, all I need is the `virtual SGMatrix<float64_t> get_multiclass_E();` method in `CInferenceMethod`. This method is used in `CGaussianProcessMachine` class.