SQL support instead of Firebase

[Reterics]

As an alternative and/or PHP hosting support, we need to have SQL support as well.

Solution proposal

DatabaseManager -> DatabaseModel (SQL and firebase)

1. Cloud based SQL Support: https://cloud.google.com/sql (PHP hosting support+)
2. Introduce SSR in project with API endpoints + ORM (Sequelize)
3. Separate PHP API endpoint (PHP hosting support+)