Use FullPath for the selected data sources query

Summary:
Makes for a more valuable grouping of the projects when using server
based resources, since all the project groups on the same server will
be listed after one another.

Obviously impacts what is seen through the available pages model so need
to adjust the feature tests accordingly.

Reviewers: bensi, dfaure, franckarrecot

Differential Revision: https://phabricator.kde.org/D7055