Fixed supply planes being able to attack with bombs

Fixed several bugs regarding flanking bonuses because I misinterpreted how flanking bonuses are applied in-game (oops)

Expanded "Conquer the World" campaign

Fixed General in CtW spawning as Devastator

- Added three new endgame units, unlocked by researching AI technology: Assault Drone, Line Trooper and Machine Warrior
- Updated script used in CtW to the new, more performant version
- Experimental balance adjustments to endgame units

- fixed Tachankas crashing the game
- adjusted combat stats of the Tachanka

- increased resource output provided by resource upgrades
- changed upgrade costs to mostly wealth, metal and knowledge instead of wood or food

- fixed low maximum garrison power for Forbidden City

- Fixed missing attack move for Fluyt/Clipper
- Changed time to train Slingers to be longer, reduced their attack from 9 to 8 and added a gold cost of 2 to their existing cost
- Spanish get less starting scouts and less resources from ruins
- Changed description of Germany to more accurately explain that they only get free metal production upgrades if they have the science level that is normally needed for them