Make terraform unique triggerable from improvements

By SomeTroglodyte:
- Right-click/longpress for World screen city buttons 
- Unit actions from Uniques shouldn't be active at zero movement 
- Fix double "close" action from Overview ESC key 
- Fix a few applications of the "hidden from users" modifer 
- Fix fortified units upgraded to ones that can't fortify still keeping their fortification 
- Fix options setting for the notifications scroll visibility being wrong for new installs 
- Change EmpireOverviewScreen closing to use the same button and UX as Civilopedia 
- Normalize TNP 'search' links, fix a few broken or incomplete attributions 

Added unit escorting formation!!!  - By tuvus

Allow conditional timed triggers for unit actions or most other trigger conditionals  - By SeventhM

Allow Barbarians to make set-up ranged units  - By SpacedOutChicken