Handle lane_ids in workflow creation and update.  Added method to find distinct lanes .get_lane_ids
.create_workflow method will always add lane_id to workflow xml.  Defaults to 'default'
.get_objects_for_workstep now has lane_id as an expected parameter with a default value of 'default'

repository and workflow are now optional params
Merge pull request #3 from sul-dlss/feature-lane-ids

Handle lane_ids in workflow the workflow service