#15 ~/.kahakai/user.style to override chosen style

[Evgueni Pervago]

Currently there is no way to set your own wallpaper and
wallpaper is set only in styles which means you have to
edit the style file if you want to keep your current
wallpaper. That's annoying.

I propose a user.style file which will contain
(commented out by default) style settings which will
take priority over chosen style.