specifying context to GetProperty and SetProperty

[jmuk]

Hi,

So there are Call and CallWithContext for dbus.BusObject. The former is actually a proxy of the latter with context.Background. However, GetProperty and SetProperty don't have such variations and they always use context.Background. It would be plausible if we have something like GetPropertyWithContext and SetPropertyWithContext with custom context.

[jsouthworth]

It is feasible to do this. GetProperty and SetProperty are just wrappers around Call so one can use CallContext in the same way https://github.com/godbus/dbus/blob/master/object.go#L200.