mark.whicker@langnews.com @MWhicker03LANG on TwitterThe National Baseball Hall of Fame opened its first Unicorn Wing on Wednesday.Its curators will blink in befuddlement when Mike Piazza walks in.What is this? An everyday catcher? Who hits home runs? And hits for average? And limits his strikeouts? And handles the league's best pitching staff?Obviously this exotic creature has been assembled from leftover parts, like a jackalope.