Add support for configurations override

[Zoey76]

As a server owner I want to be able to configure certain server settings without having conflicts with default configuration changes, this settings must override default configurations.

1. Default files WILL document which configuration exist.
2. Custom config files WILL overwrite configs loaded from default files.
3. Override file always take priority over default configuration
4. Automated server update MUST be possible without conflicts or file merging.
5. Server MUST warn about deprecated or deleted configs which are present in the overwriting config.
6. GUI tool MUST support configuration editing and comparing with default values.
7. Files MAY have "section" INI style.

[Zoey76]

Already done in configuration rework.