Add option to log requests

[siebrand]

Logging is disabled by default. When logging is enabled, log files will be rotated daily.

Settings added:

• logRequests: boolean: Whether requests should be logged. Default: false.
• logFile: string: File to log requests to. Default: requests.log.
• logMaxFiles: integrer: Number of log files to keep. Default: 31.

Library used: https://www.npmjs.com/package/logger-request