Chore: Housekeeping

[adzialocha]

First "housekeeping" steps for upcoming improvements and changes to the codebase:

• Render index.html via pug on server-side for easier customization
• Change build system from gulp to webpack
• Update deprecated sequelize methods
• Update all dependencies and asset building pipelines (Babel, scss etc.)
• Replace outdated react-router-redux with connected-react-router
• Introduce LOG_LEVEL env variable for more control over logs, improve winston logger