Allow to define number of Retries for WIH exception handling strategy.

Currently customer is using 'RETRY' handling strategy to handle the exception with REST workitem handler.

new org.jbpm.process.workitem.rest.RESTWorkItemHandler(classLoader,"error-handlingProcess","RETRY")

Currently engine try to re-execute the REST WIH 3 times as its values is hard coded in AbstractLogOrThrowWorkItemHandler. Customer want to change this default retry attempts.