Type-safe Invasion status

[programaker]

Draft of the idea - https://scastie.scala-lang.org/programaker/QzbOoPCxTIuCvlXhWyUPBA/8

GameProgress.start should accept only defeated Invasions.
defeated flag will be removed and replaced by type checking.

[programaker]

To make it really safe, GameProgress changes proposed in #4 are necessary, otherwise we can't handle Invasions with different statuses inside the same GameProgress. We'll need a Start game progress with only Active Invasions and a InBattle progress with mixed