add localization and internationalization into marvin-web

[havok2063]

Using Flask-Babel and Flask-Phrase (Phrase App), add localization and internationalization support into Marvin.

Examples: https://damyanon.net/flask-series-internationalization/ https://phraseapp.com/blog/posts/python-localization-for-flask-applications/ https://blog.miguelgrinberg.com/post/the-flask-mega-tutorial-part-xiv-i18n-and-l10n