Define and fill the compatibility matrix to check OAuth2 together with different apps

[SamuAlfageme]

In light of reports like #105 or issues scattered on different app's repos (e.g. "guests' whitelisting": owncloud/guests#171); some sort of compatibility matrix should be filled to document which applications are currently supported and working together with the OAuth2 plugin.

It can be considered part of owncloud/QA#498 as "integration with other apps".