Districts' integration: 'Town', new Grown Infrastructure

Population instances are to be considered fix sized blocks called district of a Town object. Now integration of neighbor districts to one Town is made possible. Also different population owner groups can name their town and district upon settlement. We'll just need a better world map that shows town names to make it funnier later. :)

I've implemented a new AbstractInfrastructure extension called GrownInfrastructure. In this one things are grown together from block to block flowing in random direction inside a Population. It looks better than just shuffled DefaultInfrastructure.