Fetch application description property and Fetch Item references

Adding property  `appDescription` in `PKTApp` class.
Adding `fetchItemReferencesWithID` method in `PKTItem` class.
Sorry, but i don't understand how you want to do that. The webservice return un array of linked Applications, and inside it un another array called "items". My first intention was return all items in a simple array, not a multidimensional array.