Config server with settings

Added setting interface (ServerSettings and ServerInternalSettings) for server to access its configuration properties.

Enabled to obtain a server property with Config.get + property settings. Replaced the previous Apache Configuration + constant string property-accessing-pattern. 
That's awesome - however, we should also have tests for the user-level behavior here, ensuring that, from the outside, when the user changes these settings, the server behaves as advertised.