Disable "Back" to "Review & Deploy" step if deployed

[fionnachan]

I was on the "Download" step, then clicked "Next" to the last step "Deploy Locally"
But I wanted to navigate back to the "Download" step, and accidentally clicked "Back" also on the "Download" page

It brought me back to one step before (correctly, but it was a user mistake to click the "Back" button)

And now there is no way to view the config at the "Download" step, or the "Deploy Locally" information

And clicking "Deploy" would do nothing

Things to do on the UI:

1. do not allow users to go "Back" from the "Download"step
2. allow users to navigate to and from the final 2 steps by clicking the steps