Drop dependency on Commons Codec by native MD5 digest call

[reinouts]

Proposed implementation of Utils.getMD5Hash():

public static String getMD5Hash(String jsonString) throws UnsupportedEncodingException, NoSuchAlgorithmException {
    byte[] bytesOfMessage = jsonString.getBytes(RestServices.UTF8);
    MessageDigest md = MessageDigest.getInstance("MD5");
    return new String(md.digest(bytesOfMessage));
}