code: public void setEncoding(Encoding encoding) {
  		replace(ENCODING, (encoding == null) ? null : encoding.getValue());
  	}
docs: <p>
  Sets the ENCODING parameter value.
  </p>
  <p>
  This parameter defines how the property value is encoded (for example,
  "base64" for a binary value).
  </p>
  @param encoding the encoding or null to remove
  @see <a href="http://tools.ietf.org/html/rfc5545#page-18">RFC 5545
  p.18-9</a>