By Svea Herbst-Bayliss NEW YORK (Reuters) -Irenic Capital Management built a sizable stake in Workiva, arguing the financial reporting software maker needs to improve its operating efficiency, refresh its board and consider a potential sale. Irenic owns roughly 2% of Workiva and has met with management numerous times to discuss possible changes to help the $4.7 billion company perform better, according to documents seen by Reuters and two people familiar with the matter. Specifically, the New York-based ...