Tech screen performance improvements

Notification for city conversion when removing heresy

Fixed unique buildings/improvements with zeroed stat not showing before vs after

By sulai:
- Show "x units due" on Big Button, setting for cycling units 
- Constructions table: avoid vertical movement of lower table 

Added option to change the Maximum Autosave turns stored - By Emandac

Add hotkey for Idle Unit cycle buttons - By itanasi