Add the basic flags
Add the basic properties and create the overlay behavior for Flyouts
Remove ShowWindowButtonCommandsOnHiddenTitleBar and replace it with the new overlay behavior
Use the HasFlag method
Create the titlebar overlay behavior for all elements
Don't overlay the icon by default
Move test helpers around
Fix up the Flyout tests
Move that to Controls
Ensure that we don't break backwards compatibility
Rename it to "WindowCommandsOverlayBehavior"
That shouldn't be here
Merge pull request #1427 from MahApps/windowcommand-flags

TitleBar element overlay flags