Diplomacy:
Player can now be contacted by other civilization (that have already been met).
Other civilizations react to troops bordering cities, and incursions, and have different behavior depending on civilization aggressivity setting.
(screens contains WIP elements, and debug text that won't appear in final version)
Borders:
Added border management for cities. Squares within borders can be exploited by city.
Bordering troops, and incursions are taken into account for diplomacy.
(screens contains WIP elements, and debug text that won't appear in final version)
Tutorial:
Creation of tutorial to help player understanding game mechanics (screen contains WIP elements, and debug text that won't appear in final version)
Barbarians and walls:
Barbarians can now appear on map at game start.
Barbarians have random behavior defined at game start (aggressive, neutral, friendly, etc).
Cities can now build walls to protect urbanized sectors.
(screen contains WIP elements, and debug text that won't appear in final version)
