Nobody’s writing any songs about Irish Continental Group, the company that owns Irish Ferries and Ireland’s biggest freight shipping business. But for more than thirty years, it has quietly been one of Ireland’s best-run companies. Including dividends, returns to shareholders since 2003 come to a little over 700 per cent, for a compound annual return of 12.3 per cent.  ICG is best known to the public for Irish Ferries, which sails at least 72 times per week between Dublin and Holyhead, 28 times per week between Rosslare and Pembroke, 8 times per week between Dublin and Cherbourg, and now 68…