dbus: Add getter for WPS properties

[Sven Neumann]

With the old DBus interface we have been able to access
the WPS IE of a BSS. This allowed us to scan for an 
access-point that is actively doing WPS-PBC. The new,
albeit much nicer, DBus interface does not provide means
to do that.

I am sending a patch that we are now using successfully that
adds a getter for the WPS properties of a BSS. It exposes it
as a vardict. Currently this dict only contains a "Type"
entry that can be empty, "pbc" or "pin". Other information
could be added here if it turns out to be useful.

I hope you like the patch and consider it for inclusion.


Regards,
Sven