Release 0.2.0

Created by: seliverstov

• Multilingual and english BERT-based models for classification
• Knowledge base based Question Answering model
• Refactor train script to class to simplify its modification and extension
• Super-convergence keras model class
• +3 F1 for speller correction with new custom vocab_penalty property for searcher_component
• Refactored FAQ Skill
• Add universal method destroy in Component class
• --no-default-skill optional flag if your component implements an interface of DeepPavlov Skill
• --stateful and --multiinstance flags for Amazon Alexa integration
• Move utils module from project root in to deeppavlov module
• Many minor improvements and bug fixes, including logging, Elmo save/load and many other