Handle host changes

[hadley]

After #754 is merged, we'll have the capability to follow redirects and hence determine if a connect server has been moved. It's fine to just redirect only the path has changed, but we should require user confirmation if the hostname has changed. This is probably best accomplished as pre-flight check in deployApp().

If the hostname has changed, need to:

• Confirm it's ok with the user. (Or error if not interactive)
• Create a new server with updated name and url.
• Update the old server with a field indicating that it redirects to a new server.
• On deployment, detect that the server has been redirected and update deployment record with new details.

[hadley]

Somewhat connected to #49