Unit turn damage is now serialized and saved.
Healing block promotion and Horn discover range.

Introduces another new column to the UnitPromotions table that allows
promotions to prevent passive healing from occurring.

Initial Horn of Valere discovery 'radius' implementation. It's a bit
temperamental at the moment.
Units who are heal blocked by promotions can no longer start the 'heal' mission.
Ranged Horn of Valere discovery now works and is configurable via XML. (No thanks to Database::Results's syntax.)