Support for groupings in group import

Test 1 (No regressions) Create a group import file as detailed at http://docs.moodle.org/23/en/Import_groups Go to the group import page in a course and upload the file Check that the groups have been created without errors, and no PHP notices have been shown Test 2 (New functionality) Create a group import file as detailed at http://docs.moodle.org/23/en/Import_groups . Make sure the file has at least a dozen groups. Add a column called "groupingname" and assign groups to groupings of 3 groups Go to the group import page in a course and upload the file Check that the groupings have been created (once each) and that the correct groups have been assigned to them