CPU performance improvements

UI: 
- Better "close unit table" button 
- Better options checkboxes, slider buttons, multiplayer server UI  - By Toxile

Bugfixes:
- Buy button active when civ can purchase items in puppets
- Paused music no longer resumes on game resume

By SeventhM:
- Unified unique for gaining stats/stockpiles 
- Pantheon cost respects game speed modifer 

AI: 
- Better Food Weights for citizen management - By itanasi
- Prevent incorrect settler retreat - By EmperorPinguin