CRM-11606 Warn users about unsaved changes in form designer

tim, I was inspired by this article to try to reduce our use of warnings:
http://www.alistapart.com/articles/neveruseawarning/

What do you think of the following from a ux perspective:

• When you close the dialog a CRM.alert pops up saying "Your changes to xxx profile have been discarded. Click here to undo"
• When you click the red x to remove a field from the canvas, a similar alert pops up saying "Field xxx removed. [undo]"

Since these things can be held in memory both might be fairly easy to implement.
As for the window close issue, I suppose that will still have to be a confirm()

From UX perspective, agree that undo sounds better than warning.

For CRM.alert, the timing of the auto-close for the alert may be a bit finicky. On one hand, you don't want to close too quickly or the user won't have a chance to undo. On the other hand, if you do a popup for every field deletion, then you don't want those popups to hang around too long (because they'll get annoying). But maybe there's a simple solution.

From an implementation perspective, the undo makes me more nervous... we don't really have a way to estimate it, and the warning popup is really simple (eg "confirm" or "CRM.confirm"). What you might do is take a stab at implementing undo but set a fixed time limit (like 30-60 min); if it's not reliably working after 30-60min of dev time, then skip it... the "undo" goes on the wishlist and we use a "confirm" for now.

Added undo when closing dialog and warning when leaving page.
Not tackling the field-level undo for now.