Add settings to ignore date/zone/GRF when placing houses in scenario editor

See: #177

src/settings_type.h

@@ -662,6 +662,9 @@ struct DebugSettings {
 /** Scenario editor settings. */
 struct ScenarioSettings {
 	bool multiple_buildings;                 ///< allow manually adding more than one church/stadium
+	bool house_ignore_dates;                 ///< allow manually adding houses regardless of date restrictions
+	bool house_ignore_zones;                 ///< allow manually adding houses regardless of zone restrictions
+	bool house_ignore_grf;                   ///< allow manually adding houses regardless of GRF restrictions
 };
 
 /** All settings together for the game. */