Confirmation before posting weight values that'll generate an email

Currently, if Alyx receives a weight entry for a mouse that is below 80%, it sends a warning email to the experimenter and to Charu. This is very often a false alarm, either because of a typo or because the user has weighed the wrong mouse.

The feature request is for a pop-up box to appear in these cases, asking the user to confirm the weight they're about to post. Specifically, if in AlyxPanel I select a mouse and click "Manual Weighing" then enter a weight that's too low and press "ok", a box should appear saying something like "You have entered $weight for $mousename. Please confirm that this is the correct weight for this mouse" with an "confirm" button that posts the weight and a "cancel" button that takes me back to enter a new weight.

It might also be useful to ask for confirmation in other cases that're likely to be errors, like if the weight of the mouse is outside some band around the recent average weight, or if the mouse has already been weighed that day.