Support deploying cloud server from mobile uProxy Air client.

Using an Android web view in our app, we can improve the cloud deployment in ways that aren't possible in a standard web page.

We should:

• Ensure new website to deploy cloud servers (Build website to deploy cloud servers #2824) is mobile friendly, using responsive CSS design.
• Inject CSS into DigitalOcean payment info page to make mobile friendly, and possibly push users towards PayPal
• Skip the droplet creation step
• Detect when the user verifies their email with DigitalOcean and open the verification link inside uProxy, so they don't accidentally end up in a Chrome browser instead
• Update our install instructions on mobile (we may be able to simplify the instructions and remove references to droplets)