[Zones] Convert IDLE_WHEN_EMPTY to a Zone Column (#3891)

* [Rules] Convert IDLE_WHEN_EMPTY to a rule

# Notes
- Converts `IDLE_WHEN_EMPTY` to `Zone:ZonesIdleWhenEmpty` so that we can change this on the fly or on a zone-by-zone basis instead of having to recompile to do this.
- Especially helpful for those using release binaries that do not compile their own source.

* Convert to zone column.

* Update ruletypes.h

* Update ruletypes.h

* Update entity.cpp

* Update entity.cpp

* Rename.

* Update database_update_manifest.cpp

* Update base_zone_repository.h

* Update zone.cpp

* seconds_before_idle

* Update database_update_manifest.cpp

* Getter/Setters/Private

* Update base_zone_repository.h

* IsIdle()/SetIsIdle()

* Update entity.cpp

common/features.h

@@ -35,11 +35,6 @@ Core Zone features
 
 */
 
-
-//Uncomment this to cause a zone to basically idle
-//when there are no players in it, mobs stop wandering, etc..
-#define IDLE_WHEN_EMPTY
-
 #ifdef EMBPERL
 //Enable the new XS based perl parser
 #define EMBPERL_XS