Feature - Add delays (fixed or random in range)

[DSaunders]

Add a fixed delay to a response, either:
A fixed time (written as human readable, e.g. 3 seconds) or

"response": {
  "delay": "3 seconds"
}

or a random time

"response": {
  "delay": {
    "from": "1 second",
    "to": "3 seconds"
  }
}