Changed tech trigger to accept tech filters

By SomeTroglodyte:
- Improve DiplomacyScreen UX (nation icons) on cramped screens
- Move DiplomacyScreen close button to top right
- Validation warning Suppression as Unique or modifier
- UI: Fix options popup "spilling" in cramped screen conditions

Allow city state uniques for nation descriptions  - By SeventhM

Add MovedToNewCapital buiding unique  - By PLynx01

Better military unit retreat  - By tuvus