fix(rest/deployment): fix deployment REST resource

- rename "/deployments" resource to "/deployment" as other
  REST resources are singular
- add missing deployment resouces REST resource
- reword some parts

related to #CAM-2084, #CAM-2085, #CAM-2086, #CAM-2087, #CAM-2088
feat(rest-api): Extend Deployment docu

POST /deployment/create
     create new deployment

related to #CAM-1375