Show Unciv icon when loading game, instead of happy face

AI: Recognize when no further techs can be researched, even if some techs are blocked

Don't re-raise tech popups for previously researched techs

By xlenstra:
- Fixed bug disabling pantheon founding

UI fix - By GGGuenni

Add "UI Skin" to make it translatable  - By Ouaz

Fixed bug on 'resume game' - By nacro711072