Set lot winners screen should be more responsive

[iragm]

The following changes would make the set lot winners screen better:

• A button to go into full screen mode (requires a div for the form and all related stuff so the page doesn't reload)
• AJAX update field statuses with issues like lot not found, user invoice closed, etc.

[iragm]

If the lot has a reserve price set, there should be some kind of friction if you try to sell the lot for less than the reserve.
From #181:

This should launch a prompt (reserve price is $x, are you sure you want to sell for $y).

[iragm]

If the auction is in-person and bidding is allowed, add in information discussed #189 (comment)

[iragm]

Should be pretty easy to post a message in real time to the lot page when a lot is going up for auction (view_lot_simple) and when it's sold, too

[iragm]

This project spiraled as things tend to:

• Lot page now updates in real time as winners get set
• When setting lot winners, there's a new button to ignore errors and save
• Users that watch items in an in-person auction now have the ability to get push notifications when bidding starts on a lot
• Invoices are recalculated immediately instead of a few seconds later (previously this was done in the task that ends auctions)
• A per-user websocket connection is now available on all pages, although it is currently disabled, it may be handy for future improvements