UI config file is a json format with following possible parameters:

Note: All top level keys must be optional.

"download_screen" (depends on "network_screen")
	Used to show a window where user can input a custom URL from
	which a file can be downloaded and placed in a custom location
	in the installed system.

	"title" (required)
		A short title to identify this screen
	"intro" (required)
		An brief 2 line intro of what URL you are requesting the
		user to input
	"destination" (required)
		String; Path to where in the installed system you would
		like to see this file
