Add Font.OPEN_SANS.
Update IDEA project files.
Create SliderDemo example

An example of building a custom UI component with non-trivial interactions.
Replace Point constructor with Point.at()
Add ClickReceiver.move, and implement it for uilayer-swing
Change ClickReceiver.click(Rect, x, y) -> ClickReceiver.click(Rect, Point)
Update geometry submodule.