Link URI re: issue #486

The proposed changes address the silent failing of adding a link to an unrecognized URI. They allow the user to correct any potential mistakes made to the initial address through a prompt dialogue. 
Sorry if this is right in front of me and I can't see it - but the brace on 457 closes out `if (!title)` on 442. If I add another right-sided-brace, this will close out `linkFromURL` on 436 and deprecate the workaround for a PDF url.