[FTP] make the pull callback emit progress callbacks
[FTP] make the pull callback emit progress callbacks

The progress callbacks are throttled to at most once per second to not
overload dbus for very fast connections. This is implemented somewhat
ugly using a cancellable that interrupts once per second to ensure
progress updates are sent.
If someone knows a saner approach, please tell me (or better: provide a
patch).

xkahn/gvfs-cmis,gicmo/gvfs,cpatulea/gvfs,thiblahute/gvfs,xkahn/gvfs-cmis,philipl/gvfs,xkahn/gvfs-cmis,halfline/gvfs,philipl/gvfs,gicmo/gvfs,gicmo/gvfs,philipl/gvfs,cpatulea/gvfs,halfline/gvfs,thiblahute/gvfs,gicmo/gvfs,xkahn/gvfs-cmis,halfline/gvfs