Core/Game: Add a dynamic script reloader which reloads scripts modules on changes.

* is responsible for registering plain modules.
* requires compilation with the `WITH_DYNAMIC_LINKING` flag.
* requires further support of the ScriptMgr.

(cherry picked from commit bc0f2b6e5a)

src/server/worldserver/Main.cpp

@@ -39,6 +39,7 @@
 #include "InstanceSaveMgr.h"
 #include "ObjectAccessor.h"
 #include "ScriptMgr.h"
+#include "ScriptReloadMgr.h"
 #include "ScriptLoader.h"
 #include "OutdoorPvP/OutdoorPvPMgr.h"
 #include "BattlegroundMgr.h"
@@ -271,6 +272,7 @@ extern int main(int argc, char** argv)
     sOutdoorPvPMgr->Die();
     sMapMgr->UnloadAll();                     // unload all grids (including locked in memory)
     sScriptMgr->Unload();
+    sScriptReloadMgr->Unload();
 
     // set server offline
     LoginDatabase.DirectPExecute("UPDATE realmlist SET flag = flag | %u WHERE id = '%d'", REALM_FLAG_OFFLINE, realm.Id.Realm);