Create Encoding step

[diegomarvid]

This solves the notion card Implement default passthrough encoding step

At the moment:

• Target Encoding for high cardinality features.
• Ordinal Encoding for low cardinality features.
• Passthrough for numeric features.

To Do:

• Personalize encoding selection in config.json
• More advanced encoding for high cardinality features. For later on according to @Ludecan

I had to change some lib structure to address the need to save the fitted encoders for prediction if we don't have the target. Now we save the data container with some important keys and load them from prediction. Like it was some time ago.