Fixed normal new window in kiosk mode.

If vimb is started in kiosk mode and a link is opened into new instance, the
new instance was not in kiosk mode because of missed -k option.
Use G_OPTION_ARG_FILENAME for -c option.

To use G_OPTION_ARG_FILENAME instead of G_OPTION_ARG_STRING is important
according to the glib documentation.
Changed option --fifo-name into --fifo.

The fifo with given name could not be used for new spawned vimb instances,
because each instance needs it's own fifo. To not make the things to
complicated the fifo is now always named vimb-fifo-{pid}. This allows to use
the fifo also for new spawned instances.
To get the right fifo path on startup the -d or --dump option was added to
print the full fifo path to stdout.