Throw an error if the monitor ID is not passed to zones/add/
Don't set coords to an empty value
Add the number of coords to NumCoords
Round the x,y coords of the click in the canvas
Add the x,y coords to the ZoneNumCoords input as they are clicked
Basic editing and adding zones now works.

Work still needs to be done in the view to display presets, change
elements depending on type (e.g. pixel vs. blob)