Refactor translation files

- Add prefixes to all message keys to provide context
- Use messages with attributes for some UI elements (dropdowns, dialogs, checkboxes, menus)
- Rename some class fields for consistency with translation keys

OpenRA.Mods.Common/Traits/Render/CustomTerrainDebugOverlay.cs

@@ -31,7 +31,7 @@ namespace OpenRA.Mods.Common.Traits
 		const string CommandName = "custom-terrain";
 
 		[TranslationReference]
-		const string CommandDescription = "custom-terrain-debug-overlay-description";
+		const string CommandDescription = "description-custom-terrain-debug-overlay";
 
 		public bool Enabled;