Implemented official ammo equip behavior (#3438)

* Fixes #1155.
* Added specific checks for weapons when equipping ammo.
* Ammo is removed if the required weapon is removed.
* Added battle configs to disable behavior.
Thanks to @Atemo, @exneval, and @benching!

conf/battle/battle.conf

@@ -141,6 +141,14 @@ delay_battle_damage: yes
 //     skills should consume ammo when it's acquired via a card or plagiarize)
 arrow_decrement: 1
 
+// Should ammo be unequipped when unequipping a weapon?
+// Official behavior is "yes".
+ammo_unequip: yes
+
+// Should a suitable weapon be equipped when equipping ammo?
+// Official behavior is "yes".
+ammo_check_weapon: yes
+
 // Should the item script bonus 'Autospell' check for range/obstacles before casting?
 // Official behavior is "no", setting this to "yes" will make skills use their defined
 // range. For example, Sonic Blow requires a 2 cell distance before autocasting is allowed.