Attempt to load program icon

Fix icon import in util.py but set_icon_list make the program terminate with a
core dumped.
Fix TypeError in pixbufcache
Update FIXME
Correct ShadowType
Cache is not functionnal

Disable the take of pixbuf from cache since it does not work properly.
Fix method and property

Some property were still from GTK2. We now use the ones from GTK3.
Disable swich screensaver status