This implements the title_format command, with a new placeholder %shell
which gets substituted with the view type (xwayland, xdg_shell_v6 or
wl_shell).
Example config:
for_window [title=".*"] title_format %title (class=%class instance=%instance shell=%shell)
Implements rendering of borders. Title text is still to do.
Implements the following configuration directives:
* client.focused
* client.focused_inactive
* client.unfocused
* client.urgent
* border
* default_border
Replaces arrange_windows() with arrange_root(), arrange_output(),
arrange_workspace() and arrange_children_of().
Also makes fullscreen views save and restore their dimensions, which
allows it to preserve any custom resize and is also a requirement for
floating views once they are implemented.