fix #102, add new BuiltInExpandableViews project

Besides adding screenshots and example code for the multitude of other simple ListViews, it is also necessary to show how to create expandable list views, and that requires sample code that subclasses BaseExpandableListAdapter instead of BaseAdapter. So, BuiltInExpandableViews is a new project that does that. I've added it to the BuiltInViews solution, and pushed the original BuiltInViews project into a sibling project folder.