Add description and website_url columns to oauth_apps

[alrocar]

Take into account oauth_apps are synced with central so we might want this new columns in both places.

We should include the columns to the list of public data (for granted_oauth_apps)

description is meant to have three or four lines explaining what the OAuth app is about.
website_url will be used whenever we need to redirect a user to the oauth app to log in or to get any kind of information about it.

[alrocar]

Also include icon_url as public data.