Update 0.4.19

Update 0.4.19 introduces game statistics.

Features:
- Game statistics are now available at the end of the game
- Statistics are also available for observers and in replays

Gameplay:
- Barrel and poison flask damage now correctly counts for combat fame

Mission:
- Techtrees no longer open for unfinished structures

Modding:
- Resolved a crash that could occur when importing invalid files