Add force refresh (alt version)

[thorst]

This is a slimmer implementation which doesn't keep a global list of open window handles.
The downside to not having a local array of handles, specifically in chrome, is that it
loses its original handle, and although it semi regains it, it is no longer seen as the parent.

With #12 you will get this behavior when the main page is reloaded. But under normal use
you will still be seen as the parent.

In #12 I define a global array of window handles that gets attached to the $.popupWindow
object. I believe this adds speed and is cleaner. However, its not necessary in order to regain a
reference to an existing pop up.

See #12 for all the other details.

[lencioni]

Thanks for sending these pull requests. I don't think I'll have the time to properly review these for a while, and this is @mkdynamic's project anyway so it would be great if he could check it out and decide what to do anyway.