v5.2 - Improved API token handling

• When the API Token is invalid, the script will print a better error message.

• There is a new --verify-token option to check if the token is valid beforehand, which lists the zones the token have access to.

• Added --api-token-file option: You can now read the API Token from a file.
  The file should contain only the token, without any newline characters.

  Thanks @jfly for this feature!