Introduce json schemas, alter scorefeedback model

Alters:
- nullable 'client_app' column
- expl_key -> expl_id
Fix score feedbacking for hatbot.js
New chat logging format, see schema
Fix mismatched explanation response (title->word)

This is needed because of special meaning of 'title' keyword in some json scheming standards.
Merge pull request #15 from hatbot-team/json-schemas

Json schemas