Implement delete suspects

CaseServlet
(+) Implement delete Suspect From Case
(/=) don’t use literal for category parameter

CaseDatastore, CaseDatastoreInterface, DatastoreInterface
(+) Implement deleteSuspectFromCase
(/=) consistently return false from a modifying query
ModelObjects implement Serializable

ModelObject
(+) implement Serializable so that the web server can save the model
objects that are in the session to disk and restore them