Show progress bar in subscriptions loading dialog

[nicholaschiang]

I should show a progress bar or progress numbers of some sort that indicate how many of the 1000 messages have been fetched. It would probably look like a little progress bar on the top of the LoadingDialog with some small text below it that is updated every time SWR fetches data for a new key (i.e. every time a page of 100 messages is fetched).