[Quest API] Add secondstotime(duration) to Perl and Lua. (#1281)

- Add quest::converttime(duration) to Perl.
- Add eq.convert_time(duration) to Lua.

zone/questmgr.h

@@ -369,6 +369,7 @@ public:
 	bool DisableRecipe(uint32 recipe_id);
 	void ClearNPCTypeCache(int npctype_id);
 	void ReloadZoneStaticData();
+	std::string secondstotime(int duration);
 
 	Client *GetInitiator() const;
 	NPC *GetNPC() const;