Fix WM_CLASS and WM_WINDOW_ROLE properties
Instead of forcing class and instance names, which is what GTK does by
default anyway, allow the user to set the instance name, but keep the
general class as “Surf”.
Is we won't support a “-name” parameter and don't implement a parsing of
RESOURCE_NAME env variable, let's fallback on the third behaviour, use
the name of the calling executable.
That would let the user do things like 'ln -s ./surf ./surf-other;
./surf-other' and set different parameters for the two instances (in dwm
for example).
Try to generate a unique WM_WINDOW_ROLE (within the surf process)
composed of “Surf” and the view ID.
