OOP Data loading

The data ist now dynamically loaded from the file "data.xml". This makes it easy to add or edit the data.
In addition, two new classes were introduced, PersonData, which holds the Data in an Object form and PersonDataProvider, which reads the data from the xml file and creates new PersonData objects from it.

Also, glue code was added into Form1 and the unneccesary switch was replaced by a more dynamic way.