Dialog windows open conditionally

Clicks on the dialog buttons do not call the `.exec` function—they call the `.dialog` function, directly, bypassing `.exec`.

Bypassing `.exec` is ok because `.exec` seems like an artificial nexus, where all commands seem to go through, which there doesn't seem to be a purpose for. Such a nexus is in itself doesn't seem very useful to me. I don't see a justification for such a design, unless something is hooked to `.exec`, making use of this kind of design. That isn't the case. And hooks can be created without such a design, using jQuery events or whatever.

Even if we decide that we like such a design, where all manipulation actions go through a single function (`.exec`), opening of dialogs isn't a manipulation action, yet.