QLButtons should be able to pop Confirm dialogs
Summary: QLButtons (and links) are very powerful, and can do arbitrarily dangerous things. We often want to be able to sanity-check with the user before actually executing.
This probably takes the form of a bunch of new parameters to _QLButton:
confirm -- a boolean that, if true, will pop a confirmation dialog when pressed
confirmMessage -- the text to display in the confirmation dialog. Defaults to "Are you sure?"
confirmButtonText -- the text to show instead of "Yes"
cancelButtonText -- the text to show instead of "No"