* Lowers earnings estimates for global software, IT companies * Expects IT cos' earnings to fall 2 pct in 2012, increase 4 pct in 2013 * Favours large caps vendors and companies that are restructuring July 20 (Reuters) - Earnings at global software and IT services companies are expected to decline by 2 percent on an average this year, Societe Generale said, downgrading several stocks, including Logica Plc and Sage Group Plc. "We expect companies to adopt a more cautious view of