Re-join call after code push causes a reload

[ebroder]

Today, if we push out code to Jolly Roger, everyone's client will refresh and anyone currently on a call will get disconnected.

My intuition is that if we were previously in a call, we should re-join the call after the page is refreshed. There are a few tools we could use to make that happen. One is Meteor's reload package, which specifically allows you to thread through data across a reload. Another option would be to use use-persisted-state along with sessionStorage, which is local to the tab and doesn't persist. (sessionStorage might make it tricky to tell if the we refreshed the page due to code updates, or if the user refreshed the page on their own, in which case we plausibly would not want to rejoin the call)

@zarvox proposed an alternative on #594:

As another point in design space for avoiding data loss during Meteor reload: Sandstorm had a scheme where if you had any grains open at the time, it'd inhibit reload from refreshing until you closed all of them or clicked on the "update available -- click here to reload" banner: https://github.com/sandstorm-io/sandstorm/blob/master/shell/imports/sandstorm-ui-topbar/topbar.js#L27-L55 . That approach makes it a bit more likely there are still old clients running around in the wild, though.