Import includes enrolment methods

1) Create 2 courses: "source" and "target" 2) In "source" add various enrolment plugins (manual, guest, self...) and add 1-2 manual enrolments (students). Add also 1 forum and ignite some discussions with those students. 3) In "target" add manual enrolment only with 1 student (different student from the ones in point 2). 4) Logged as admin, perform one import in "target", picking "source" as origin. Select the forum activity and import. 5) TEST: The operations ends without error. 6) TEST: The forum activity has been imported but without any discussion. 7) TEST: Look at "target" enrolment methods. Only the original "manual" is there and none of the enrolment methods in "source" have been imported.