Copy card link to clipboard?

[wking]

@jbenet expects this to be the result of 🔗 (U+1F517 LINK SYMBOL), and @VictorBjelkholm expects it to be the result of 📋 (U+1F4CB CLIPBOARD). But do we need direct support for this? I'd expect users to center on the card (with whatever the UI for that ends up being, #30, #45) and then copy the URL from their address bar. This issue is to sort out whether we need direct copy-URL support and, if so, what icon to use for it.

[jbenet]

I think:

• it's fine if this is left out for now -- it's not super necessary
• i'd say clipboard is better
  • (i meant that the link icon meant copy-link for people, not that the link icon is the best copy-link icon)
• we could bring this up on hover on the card, too, to avoid clutter.