Automated units don't try and conquer the same city twice

Constructed units that can't be placed are put on hold till the next turn

Solve 'desktop tries to create window of size 0/0' bug

Make AI buy city tiles.  - By WhoIsJohannes

By SomeTroglodyte:
- Untinted stat symbols in tinted text
- Moddable Civilopedia Welcome
- Fix disbanding units a civ cannot afford
- Main menu cancels background map creation when obsolete