Comment 6 for bug 1630174

You can't assume that an economy is convex. Assume that you have a map like with 2 land masses like this:

    #############################
  ###########################
#### ############
#### ##### ooooooooooo
#### ooooooooo ##### ooooooo
## oooooo ###### oooooooooooo
### ooo ooooooooooooo
#### oooooooooooooooooooooooooooooooooooo
###
################
###################

I think having it in the warehouse would be too confusing, but we could have a button in each warehouse window that will open the economy window. And while we're at it, why not have the button in each building window.