Implements clearbody, update changestatboost interface

Scripts/Abilities/AngerPoint.as

@@ -2,7 +2,7 @@ namespace Gen7 {
     class AngerPoint : PkmnScript {
         void OnIncomingHit(ExecutingMove@ move, Pokemon@ target, uint8 hit) override {
             if (move.GetHitData(target, hit).IsCritical){
-                target.ChangeStatBoost(Statistic::Attack, 12);
+                target.ChangeStatBoost(Statistic::Attack, 12, true);
             }
         }
     }

Scripts/Abilities/BeastBoost.as

@@ -29,7 +29,7 @@ namespace Gen7 {
             if (user.GetFlatStat(Statistic::Speed) > user.GetFlatStat(Statistic::HP)) {
                 increaseStat = Statistic::Speed;
             }
-            user.ChangeStatBoost(increaseStat, 1);
+            user.ChangeStatBoost(increaseStat, 1, true);
         }
     }
 }

Scripts/Abilities/Berserk.as

@@ -3,7 +3,7 @@ namespace Gen7 {
     class Berserk : PkmnScript {
         void OnDamage(Pokemon@ pokemon, DamageSource, uint old, uint new) override {
             if (float(old) / pokemon.MaxHealth >= 0.5f && float(new) / pokemon.MaxHealth < 0.5f) {
-                pokemon.ChangeStatBoost(Statistic::SpecialDefense, 1);
+                pokemon.ChangeStatBoost(Statistic::SpecialDefense, 1, true);
             }
         }
     }

Scripts/Abilities/PreventDefLowering.as

@@ -1,8 +1,8 @@
 namespace Gen7 {
     [Ability effect=PreventDefLowering]
     class PreventDefLowering : PkmnScript {
-        void PreventStatBoostChange(Pokemon@, Statistic stat, int8 amount, bool &inout prevent) override {
-            if (stat == Statistic::Defense && amount < 0) {
+        void PreventStatBoostChange(Pokemon@, Statistic stat, int8 amount, bool selfInflicted, bool &inout prevent) override {
+            if (stat == Statistic::Defense && amount < 0 && !selfInflicted) {
                 prevent = true;
             }
         }

Scripts/Abilities/PreventStatLowering.as

@@ -0,0 +1,10 @@
+namespace Gen7 {
+    [Ability effect=PreventStatLowering]
+    class PreventStatLowering : PkmnScript {
+        void PreventStatBoostChange(Pokemon@, Statistic stat, int8 amount, bool selfInflicted, bool &inout prevent) override {
+            if (amount < 0 && !selfInflicted) {
+                prevent = true;
+            }
+        }
+    }
+}