Get YouTube auth key from user input

[jmbeach]

Should use an OAuth flow to get permission to use the user's account to search YouTube. Otherwise, when I publish this to the Chrome store, I'll be abusing the limits of my account and I can't afford to pay for others to use the extension.

What I hope to accomplish is, after install, the user is prompted to login to YouTube. At the end of the login, hopefully YouTube posts the extension an API key to use which will be stored for the extensions life.

This will solve another problem which is that developers of this project have to manually configure their YouTube key. One less configuration is always good.