Add optional term descriptor to CohortYear common object

This was originally brought up by Lori @ Crocus in a TPDM review that there were some instances where a EPP would like to know not only the year a candidate was part of but also the term. 

It was just brought to my attention that a couple of the EPP's in the starter kit cohort could really use this as well, and are struggling with just the year that is provided by the current  entity.