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/Guilds/GuildMgr.cpp

@@ -15,11 +15,15 @@
  * with this program. If not, see <http://www.gnu.org/licenses/>.
  */
 
-#include "Common.h"
 #include "GuildMgr.h"
+#include "DatabaseEnv.h"
+#include "Guild.h"
+#include "Log.h"
+#include "ObjectMgr.h"
 
 GuildMgr::GuildMgr() : NextGuildId(UI64LIT(1))
-{ }
+{
+}
 
 GuildMgr::~GuildMgr()
 {