Ruleset validation refactor - easier location of affected objects, correctly display parameter-type mismatches, ignore uniques used for filtering

By SomeTroglodyte:
- Correct notifications for modded Citadel
- Music: Fix mini-player showing last track during inter-track silence
- Allow modders to hide individual Uniques from Civilopedia
- Ruins can no longer be save-scummed for better results

Fixed null reference error related to nuking  - By tuvus