Add support for configuring HTTP Server Timeout Values

See: https://nodejs.org/api/http.html#http_class_http_server

In particular, support added for:

• timeout (available when running Node v0.9.12 and later)
• keepAliveTimeout (available when running Node v8.0.0 and later)
• headersTimeout (available when running Node v11.3.0 and later)

These can be set in the "express" block in default.json as:

"express": {
    "httpServer": {
      "timeout": 111111,
      "keepAliveTimeout": 222222,
      "headersTimeout": 333333
    }
  }

This feature is also documented on the Wiki as HTTP Server Timeouts.