Doesn't allow to GET Retired Encounter Roles

The current implementation of Encounter Role REST part doesn't return the retired encounter roles through GET calls. It should also return retried encounter roles to identify those by the end user to make it unretire.
https://github.com/openmrs/openmrs-module-webservices.rest/blob/master/omod-1.9/src/main/java/org/openmrs/module/webservices/rest/web/v1_0/resource/openmrs1_9/EncounterRoleResource1_9.java#L88-L89