remove server.dev / server.core dichotomy

[fbielejec]

Problem

Server is split into two namespaces, which creates an unnecessary complexity and is a potential point of failure (irreducible builds between different environments).
Any run-time configuration is perfectly achievable using config

Implementation

Remove that dichotomy and provide one entry point for the whole application.

Acceptance Criteria

• One entry-point namespace
• No regressions