goa-authorizer: Add domains for documents if "files" is on
goa-authorizer: Add domains for documents if "files" is on

The new gvfs backend will enable nautilus and the gtk+ file chooser to
interact with Google Drive. This means that GOA accounts in Google
will get a "files" switch, which we should check when deciding whether
to enable the documents service.

https://bugzilla.gnome.org/show_bug.cgi?id=751782

GNOME/libgdata,pwithnall/libgdata,pwithnall/libgdata