Parameterize ListView, TableView and TreeView getters and setters for ListData

Firstly, please forgive me if I use incorrect terms, I'm no generics expert

I'll use TableView#getTableData() as an example. This method is today anonymously typed, so that if you want to mutate the list, you need to cast it to a spesific type first. This can easily be fixed by parameterizing the method. The same goes for ListView and TreeView as well. I'll supply a patch to change this behavior. This removes an annoyance and enables better looking code.

This is how one need to do it today:

List<MyObject> myList = (List<MyObject>) tableView.getTableData();
myList.add(myObject);

By parameterizing the methods, this changes to:

tableView.getTableData().add(myObject);