Core/Spells: spell effect handling improvements

* Call spell effect handlers in 4 modes:
   - SPELL_EFFECT_HANDLE_LAUNCH - called when spell is launched (cast just finished)
   - SPELL_EFFECT_HANDLE_LAUNCH_TARGET - called when spell is launched for each target in spell target map
   - SPELL_EFFECT_HANDLE_HIT - called when spell hits its destination
   - SPELL_EFFECT_HANDLE_HIT_TARGET - called when spell hits it's target from spell target map
*Correctly implement SPELL_EFFECT_TRIGGER_SPELL, SPELL_EFFECT_TRIGGER_SPELL_WITH_VALUE, SPELL_EFFECT_TRIGGER_MISSILE_SPELL_WITH_VALUE, SPELL_EFFECT_TRIGGER_MISSILE_SPELL
*Remove spell system hacks which became obsolete with this commit
Core/SpellScripts:
add OnEffectLaunch, OnEffectLaunchTarget, OnEffectHit, OnEffectHitTarget hooks for new effect handle modes and remove OnEffect hook.
A generic rule of thumb how to update your scripts (will work for nearly all cases) for spell system noobs:
if your spell script used GetHitXXXX function, you need to use OnEffectHitTarget, otherwise use
OnEffectHit

src/server/scripts/Spells/spell_hunter.cpp

@@ -179,7 +179,7 @@ public:
 
         void Register()
         {
-            OnEffect += SpellEffectFn(spell_hun_chimera_shot_SpellScript::HandleScriptEffect, EFFECT_0, SPELL_EFFECT_SCRIPT_EFFECT);
+            OnEffectHitTarget += SpellEffectFn(spell_hun_chimera_shot_SpellScript::HandleScriptEffect, EFFECT_0, SPELL_EFFECT_SCRIPT_EFFECT);
         }
     };
 
@@ -215,7 +215,7 @@ public:
 
         void Register()
         {
-            OnEffect += SpellEffectFn(spell_hun_invigoration_SpellScript::HandleScriptEffect, EFFECT_0, SPELL_EFFECT_SCRIPT_EFFECT);
+            OnEffectHitTarget += SpellEffectFn(spell_hun_invigoration_SpellScript::HandleScriptEffect, EFFECT_0, SPELL_EFFECT_SCRIPT_EFFECT);
         }
     };
 
@@ -250,7 +250,7 @@ public:
         void Register()
         {
             // add dummy effect spell handler to pet's Last Stand
-            OnEffect += SpellEffectFn(spell_hun_last_stand_pet_SpellScript::HandleDummy, EFFECT_0, SPELL_EFFECT_DUMMY);
+            OnEffectHitTarget += SpellEffectFn(spell_hun_last_stand_pet_SpellScript::HandleDummy, EFFECT_0, SPELL_EFFECT_DUMMY);
         }
     };
 
@@ -300,7 +300,7 @@ class spell_hun_masters_call : public SpellScriptLoader
 
             void Register()
             {
-                OnEffect += SpellEffectFn(spell_hun_masters_call_SpellScript::HandleScriptEffect, EFFECT_1, SPELL_EFFECT_SCRIPT_EFFECT);
+                OnEffectHitTarget += SpellEffectFn(spell_hun_masters_call_SpellScript::HandleScriptEffect, EFFECT_1, SPELL_EFFECT_SCRIPT_EFFECT);
             }
         };
 
@@ -345,7 +345,7 @@ public:
         void Register()
         {
             // add dummy effect spell handler to Readiness
-            OnEffect += SpellEffectFn(spell_hun_readiness_SpellScript::HandleDummy, EFFECT_0, SPELL_EFFECT_DUMMY);
+            OnEffectHitTarget += SpellEffectFn(spell_hun_readiness_SpellScript::HandleDummy, EFFECT_0, SPELL_EFFECT_DUMMY);
         }
     };
 
@@ -378,7 +378,7 @@ public:
 
         void Register()
         {
-            OnEffect += SpellEffectFn(spell_hun_scatter_shot_SpellScript::HandleDummy, EFFECT_0, SPELL_EFFECT_DUMMY);
+            OnEffectHitTarget += SpellEffectFn(spell_hun_scatter_shot_SpellScript::HandleDummy, EFFECT_0, SPELL_EFFECT_DUMMY);
         }
     };
 
@@ -489,7 +489,7 @@ public:
         void Register()
         {
             // add dummy effect spell handler to pet's Last Stand
-            OnEffect += SpellEffectFn(spell_hun_pet_heart_of_the_phoenix_SpellScript::HandleScript, EFFECT_0, SPELL_EFFECT_SCRIPT_EFFECT);
+            OnEffectHitTarget += SpellEffectFn(spell_hun_pet_heart_of_the_phoenix_SpellScript::HandleScript, EFFECT_0, SPELL_EFFECT_SCRIPT_EFFECT);
         }
 
         bool Load()
@@ -544,7 +544,7 @@ public:
         void Register()
         {
             // add dummy effect spell handler to pet's Last Stand
-            OnEffect += SpellEffectFn(spell_hun_pet_carrion_feeder_SpellScript::HandleDummy, EFFECT_0, SPELL_EFFECT_DUMMY);
+            OnEffectHit += SpellEffectFn(spell_hun_pet_carrion_feeder_SpellScript::HandleDummy, EFFECT_0, SPELL_EFFECT_DUMMY);
             OnCheckCast += SpellCheckCastFn(spell_hun_pet_carrion_feeder_SpellScript::CheckIfCorpseNear);
         }