Float window behavior when being first floated and when double clicking on title bar

Added properties to Dockpanel to specify how FloatWindows look (border style) and what they do when their title bar is double clicked (currently, they always return to their dockpanel). FloatWindow allows users to peel windows out of maximized state. They can then drag the window into a dock panel position.

I tried to make the maximize -> dock be a one step process but there isn't a good way to do this right now. Will commit again if I figure that out.