Use user.login.id as emplid

Reduces needless Wisconsin-specific-ness and makes the portlets slightly closer to local-deploy-ready by switching to use the ubiquitous `user.login.id` as the default user attribute to use as the source for the employee identifier.

Credit to @jameswennmacher for articulating this improvement; see also discussion at https://lists.wisc.edu/read/messages?id=32053450 .