Reload images when downloading or removing a mod

Better mod compatibility autochanges (remove removed units/improvements correctly)

By tuvus:
- Added 'return worker' notification
- Liberating civ grants open borders

By SomeTroglodyte:
- Reorganized World Screen Top Bar in small screens
- Allow Space Key to close 'Player Ready' screen (hotseat)

Added tests for most nuke functionalities  - By Framonti