request: add 'copy to clipboard' to saml_login passcode UI page

[kushmerick]

the primary (only?) use-case for this page to copy/paste the passcode to an awaiting 'cf' prompt. so it would be very helpful to add a 'copy to clipboard' button to the UI, perhaps something like this: http://www.htmlgoodies.com/beyond/javascript/article.php/3458851/Click-Its-Copied.htm

[jfoley]

@rmorgan Is this something that you would accept as a PR?

Thanks,
CF Community Pair (@jfoley & @jtuchscherer)

[rmorgan]

@jfoley Yes, it's a good request, added to our icebox: https://www.pivotaltracker.com/story/show/70186176