Added Expander to sampleapp.
Encapsulate MuppetsExpander in automation layer.
Unused usings.
Support for expanding Expander.
Remove redundant WpfContentControlBase base class.
Added styled Expander to sampleapp where the Header visual is difficult to find since it doesn't have the default name.
Expose ExpandButton from Expander that can be clicked instead of assuming that Click() always clicks on the ExpandButton. The main reason is that it is difficult to find the button in a generic way when the Expander is styled.
Test Expander header title.
Test for styled expander, one that hasn't got an element with name HeaderSite.