[Zone] Implement Zone State Saving on Shutdown (#4715)

* Save spawns

* Update base_zone_state_spawns_repository.h

* Zone state save work

* Code cleanup

* More cleanup

* Database migration

* Update database_update_manifest.cpp

* Revert decay at storage model

* Code cleanup

* More cleanup

* More cleanup

* More cleanup

* Entity variables

* Add entity variables to the schema

* Post rebase

* Checkpoint

* Serialize / deserialize buffs

* Current hp / mana / end save / load

* Save / load current_waypoint

* Add zone spawn protection

* Finishing touches

* Cleanup

* Update zone_save_state.cpp

* Cleanup

* Update zone_save_state.cpp

* Update npc.cpp

* Update npc.cpp

* More

* Update perl_npc.cpp

* Update zone_loot.cpp

common/repositories/zone_state_spawns_repository.h

@@ -0,0 +1,14 @@
+#ifndef EQEMU_ZONE_STATE_SPAWNS_REPOSITORY_H
+#define EQEMU_ZONE_STATE_SPAWNS_REPOSITORY_H
+
+#include "../database.h"
+#include "../strings.h"
+#include "base/base_zone_state_spawns_repository.h"
+
+class ZoneStateSpawnsRepository: public BaseZoneStateSpawnsRepository {
+public:
+	// Custom extended repository methods here
+
+};
+
+#endif //EQEMU_ZONE_STATE_SPAWNS_REPOSITORY_H