By Scott Murdoch SYDNEY (Reuters) -Australia's Macquarie Group, will repay A$321 million ($211.35 million) to thousands of customers who invested their retirement savings into the now-collapsed Shield Master Fund, the country's corporate regulator said on Thursday. The Australian Securities and Investments Commission (ASIC) has launched Federal Court proceedings against Macquarie Investment Management after it failed to act "efficiently, honestly and fairly" by not placing Shield under heightened monitor ...