Save Sender settings as well

[JuganD]

Hey, me and my colleagues are using SB explorer quite often and we've noticed that the settings in Sender tab, when sending a service bus message to specific queue, are not saved like the message content.

The Label, in particular, is what our app uses to navigate through the message types. On each start of the explorer, it falls back to 'Service Bus Explorer'.

It would be very handy if those settings are also persisted between restarts.