Add a configuration ui (help) to add oauth services

[monocursive]

If services packages are present but not configured, we should have a form allowing us to configure them.

[timbrandin]

I've postponed this @maz-dev, it would take a lot of work to make this useful with instructions right? But it would be nice with some documentation on what to configure etc, or links to some instructions for that.

[timbrandin]

@maz-dev How about linking to an external page (i.e. guide.meteor.com), instead of having instructions in every app that uses this package? Maybe a solution like the message when one haven't added any accounts-package at all.

[Elviron]

Bump

[timbrandin]

I would rather argue agains this, and adding some docs how to install this in the database.