Scripts/World: Update WorldBoss scripts for the Emerald Dragons (Ysondre, Emeriss, Taerar and Lethon) + create base "Emerald Dragon" AI

(They are still WIP, so do not consider them "workable" unless you are willing to report issues).

src/server/game/Scripting/ScriptLoader.cpp

@@ -63,9 +63,7 @@ void AddSC_wp_commandscript();
 #ifdef SCRIPTS
 //world
 void AddSC_areatrigger_scripts();
-void AddSC_boss_emeriss();
-void AddSC_boss_taerar();
-void AddSC_boss_ysondre();
+void AddSC_emerald_dragons();
 void AddSC_generic_creature();
 void AddSC_go_scripts();
 void AddSC_guards();
@@ -664,9 +662,7 @@ void AddWorldScripts()
 {
 #ifdef SCRIPTS
     AddSC_areatrigger_scripts();
-    AddSC_boss_emeriss();
-    AddSC_boss_taerar();
-    AddSC_boss_ysondre();
+    AddSC_emerald_dragons();
     AddSC_generic_creature();
     AddSC_go_scripts();
     AddSC_guards();