Add some missing methods to the BasicElementFinder
Rename WindowsMessageBox by MessageBoxFinder and move to other namespace, it just tries to find messageboxes
Rename WindowUnderTest to TestableApplication, this represents the object type much better
Rename ChildWindow by TestableWindow since it can represent any window not just child windows
Rename OpenWindow by BasicMessageBox since it is used for MessageBoxes only
Remove Window observing features
Add documentation