FRANKFURT (Reuters) - German lender Commerzbank is discussing a further 1,800 to 2,500 job cuts, business daily Boersen-Zeitung on Friday cited company sources as saying.A spokesman for the bank declined comment.Final decisions on the cuts are due to be made during strategy meetings between the management and supervisory boards at the end of September, the report said.Layoffs would likely focus on the bank's Frankfurt headquarters - in the back office, investment banking, ship finance,..