Google API / auth

[edwardsharp]

various things needed to integrate with the YT data API.

• googleauth.js work into main.js (electron)
• app directory init in main.js ( /googleauth/ or similar)
• check for client_secret.json
• prompt to open auth url, code input element & processing
• log out (delete /.credentials/youoke.json)

Integrate Google oAuth into app for things like user playlist importing/exporting. I don't think a YT API key would be needed for searches if using oAuth.

see stubs in googleauth.js & gtest.js