[style] Rename Window::hasFocus_ to m_focused
Window: Remove size params from initialize()

Instead, allow setFullscreenMode() and setWindowSize() to be called
before initializing the window.
Remove support for setting window bit depths
Remove video.bpp config key
Add a common formatting operator for DisplayMode
SDL*Window: Remove duplicate fullscreen modes

We get these because we currently ignore the pixel format and refresh
rate.
[style] Rename Window::listeners to m_listeners
[style] Rename RenderWindow::renderListeners

... to m_renderListeners
[style] Rename RenderWindow::renderer

... to m_renderer
[style] Rename RenderWindow::displayModes

... to m_displayModes
Move DisplayMode from RenderWindow.h to Window.h
Move RenderListeners from RenderWindow to Renderer
[style] Rename Renderer::Initialize()