Faster map generation

Less memory usage for large maps

By SomeTroglodyte:
- New CircularButton Widget 
- Improve recognition of GitHub url types passed to "Download mod from URL" 

By RobLoach:
- Fix Unit Stats across Vanilla 
- Fix Spaceship Parts requiring a Scientific Victory 
- Fix Unit Name Group unique type
- Allow modding of Great Prophet names

Fix incorrect target civ used to determine defensive pact modifiers - By unciv-loof

Add plus strength amount unique - By SeventhM