More documentation and some svm linear bugfixes

The code is removed from the documentation in order to show only some plots and that's all. The Linear soft margin had a bug
on the gradient computation.
Add learning rate decay
Refactor MixingPegasos to make it fit into the previous model
Expermiental version with all Model, SGD and Loss in the same place. I don't like it
Refactor to put everything again inside svm waiting for convergence and OO encapsulation again
Refactor: Add IncrementalMixing as a base class for all mixing models
Enable the use of multiple monitors. Train cleanup
Add PegasosSCA and MixingPegasosSCA
Add Simple Convex Hull SVM initial implementation