docs: fix multiple minor defects in the spec (#123)

- In GET /neworkDevices correct example for objectType query parameter.
  It only supports long enum values
- In GET /objects (and get object children) correct documentation for
  objectType and classification parameters to show they can be
  repeated
- Modify how we version the spec document itself. It is now identified
  by a commit id from the source repo.

- This commit updates v4, v5 and v6 to the respective revisions:
  - v4 is now at 3f50fe1e
  - v5 is now at dad37a1b
  - v6 is now at 5d0e5ef0