Ability to copy gateway link to the wrapping directory

> **tl;dr** This is about feature parity with old screen in IPFS Companion

Before we switch ipfs-companion to this app (https://github.com/ipfs-shipyard/ipfs-companion/pull/642) we want to ensure users won't have any feelings of functional regression.

Old upload screen in IPFS Companion opened raw listing in a new tab and some users would prefer to have that ability. There should be a way to copy link to directory listing at the public gateway.

Basically this is a feature request to have:

- "Sharing link" with `share.ipfs.io` (current one)
- "Direct link" with `ipfs.io/ipfs/..` (todo)
- This could be a second input and "copy" button similar to other sharing websites [that expose "raw" links in addition the the "sharing" one](https://user-images.githubusercontent.com/157609/50078581-a9d6a380-01e7-11e9-824c-9f223407935e.png).
- OR just a link "View on IPFS gateway" below the input with sharing one