Extract featurization from CRFEntityExtractor

[tabergma]

Description of Problem:
The CRFEntityExtractor creates features on his own. The features cannot be reused.

Overview of the Solution:
Create a new featurizer that does the exact same featurization as the CRFEntityExtractor. Do not yet substitute the featurization part of the CRFEntityExtractor with the new component.

(Needed as preparation for the new NLU architecture.)

Definition of Done:

• Tests are added
• Feature described the docs
• Feature mentioned in the changlog

[Ghostvv]

@tabergma that's done? Can we close it?