Initial hack on an underlined TabControl
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
Change DropDownButton behavior. Now its more like drop down button, not split button
Ensure that we don't break backwards compatibility
Rename it to "WindowCommandsOverlayBehavior"
That shouldn't be here
Fix some of the casts
Small refactorings
Add the TabControl underline behavior via an attached property
Of course there is room for one more TabControl!
Rearrange and add a comment
Fix an issue with the icon visibility