Upgrade yeoman generator for script-lab projects

[WrathOfZombies]

Work on https://github.com/OfficeDev/generator-office/pull/238 and improve the following

1. Support secret gists
2. Run through the list of libraries and generate a packge.json out of it
3. Save config/auth settings to .yo config
4. Add scripts for azure deployment

Also we should be able to create not only from a gist, but also from a local file (e.g,. file alongside the generator).

We also should integrate with the Script Lab publish flow, so that, on the server, publishing calls "yo office" and generates a full package in the zip file (minus calling "npm install").

We should also add a link for the server-based download to each published gist. (I.e., https://script-lab.azureedge.net/download/gist/23423423423423);