Remove unwanted (?!) keys in output jbrowse config

[dariober]

Occasionally jbrowse get-config outputs _id and __v keys:

gitpod /workspace/apollo3-annotation/jbrowse_data (create_script) $ apollo jbrowse get-config
{
  "configuration": {
    "theme": {
      "palette": {
....
  },
  "_id": {},
  "__v": 0
}

Which result in:

 apollo jbrowse set-config config.json
    Error: Failed to add JBrowse configuration — 422 Unprocessable Entity ({"message":"ValidationError: _id: Cast to ObjectId failed for value \"{}\" (type Object) at path \"_id\" because of
    \"BSONTypeError\"","error":"Unprocessable Entity","statusCode":422})

[garrettjstevens]

Closed in favor of #471