Revised NLU pipeline

[andreaceto]

Pull Request Template

Description

Switched to completely revised NLU pipeline.

• Intent Classifier upgraded into a Multitask Model that handles both intent classification and custom NER;
• Created an Hybrid Appointment Scheduling Dataset (HASD) in order to train the model;
• Added spaCy alongside duckling for classic NER extraction;
• Defined a NLU Processor to process the input into a JSON formatted file where all key information are stored for dialogue use.

Type of Change

• Bug fix
• New feature
• Documentation update
• Refactor
• Other (please describe):

Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• [] New and existing unit tests pass locally