allow editing of url in bookmarks

[alexlehm]

When adding a bookmark with the bookmarklet, it is possible to edit the url, but this is not possible with the browser extension or when an already existing bookmark is edited.
I assume the url is the primary key for the db entry, but it would be useful to be able to edit the bookmark url sometimes.

I have bookmarked an url for copy.com after joining the service and I ended up bookmarking the url with a profile id or something, which makes it kind of useless as a public bookmark. Another similar thing would be to change https to http on a youtube or vimeo url.

(With the copy.com bookmark, the view page function also display some data from the personal files dir, not sure if that is a security issue with copy.com, but it would be better if that doesn't show up inside bookie)