Agios 237

This PR is an initial OAuth2 example (Shoot) which does OAuth2 authz with GoogleDrive and Facebook.
It does not do the actual upload as we're missing AGIOS-229, but @cvasilak you've got all the ground to test multipart upload with this initial version.

To test on Google no configuration required. To test on Facebook some configuration is required as fb required client_secret we can't commit config sample.