Clearer documentation about how to industrialize Cobra models

[sandervh14]

Clearer documentation about how to industrialize Cobra models

We've received a couple of questions in the past months about how Cobra models can be industrialized. Let's interpret that as a sign that the documentation about industrialization with Cobra can be improved.

Task Description

• https://github.com/PythonPredictions/cobra/blob/master/tutorials/tutorial_Cobra_logistic_regression.ipynb: add a dedicated "Industrialization" section and move cells 41 and 42 over there + show how the preprocessor & model files can be loaded again and applied to new data.
• idem for linear regression tutorial
• add a dedicated section for industrialization in the documentation https://pythonpredictions.github.io/cobra.io/index.html ("Industrialization" in left pane's navigation menu?).