WindowServer now looks in _$HOME/.config/WindowServer.conf_ for a
configuration file that can specify a background image.
Also add default background image /usr/share/images/sample.ppm to the
base sysroot provided in the git repo.
Current implementation can create custom windows and each window has
its own framebuffer. When window wants to write its framebuffer to the
screen it will send a message to the WindowServer using unix sockets.