Devlog #1: fog of war and minimaps

Implemented fog of war and minimaps:

Fog of war:

• hides non-friendly units when the player’s units are away far enough
• visible territory is displayed by a brighter circle around the player’s units

Minimap:

• displays visible units as colored squares
• displays terrain elevation and visible territory
• clicking on the minimap moves the player’s camera to the corresponding spot on the map