Add withVars query attribute to getProcessInstance operation for finished processes

KIE Server already provides getProcessInstance operation with query attribute withVars but only for an active process instance [1]. The enhancement will add this functionality to RuntimeDataResource to be able to query completed and aborted processes including their variables.

Additionally, the changes will require to change KIE Server client and it would be nice to add functionality to both REST and JMS.

[1] https://github.com/droolsjbpm/droolsjbpm-integration/blob/master/kie-server-parent/kie-server-remote/kie-server-rest/kie-server-rest-jbpm/src/main/java/org/kie/server/remote/rest/jbpm/ProcessResource.java#L218