gvfs-move: Improve progress output
gvfs-move: Improve progress output

Rather than spamming the screen with output, rate-limit the updates and
make them display over each other.  Also calculate the speed of
transfer.

https://bugzilla.gnome.org/show_bug.cgi?id=637543

gicmo/gvfs,gicmo/gvfs,gicmo/gvfs,gicmo/gvfs