Core/Game: Include cleanup

* Mostly aimed at removing Log/DatabaseEnv includes from other headers
* Fix most packet headers including other packet headers - moved common structures such as ItemInstance to their own files
* Moved SAI function definitions to source files (massive or requiring many different dependencies)

src/server/game/AI/ScriptedAI/ScriptedFollowerAI.cpp

@@ -23,9 +23,10 @@ SDComment: This AI is under development
 SDCategory: Npc
 EndScriptData */
 
+#include "ScriptedFollowerAI.h"
+#include "Log.h"
 #include "Player.h"
 #include "ScriptedCreature.h"
-#include "ScriptedFollowerAI.h"
 #include "Group.h"
 
 const float MAX_PLAYER_DISTANCE = 100.0f;