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. 
I'm -1 on this. The Config interface deals with Setting<> instances as keys. I'd rather we have this conversion on the outside, like:

    config.get( DynamicSetting.setting( "my.key") );