title: why the avro generated java code has so many deprecated fileds
body: <p>I am using avro-maven-plugin 1.8.1 to generate java code from schema,and all the fields are public and deprecated,like this:</p>
  
  <pre><code>  public class data_elements extends org.apache.avro.specific.SpecificRecordBase implements org.apache.avro.specific.SpecificRecord {
    private static final long serialVersionUID = 2829359487251568000L;
    public static final org.apache.avro.Schema SCHEMA$ = new org.apache.avro.Schema.Parser().parse("......");
    public static org.apache.avro.Schema getClassSchema() { return SCHEMA$; }
    @Deprecated public java.lang.CharSequence timestamp;
    @Deprecated public double value;
    @Deprecated public java.lang.CharSequence op;
  ...
  }
  </code></pre>
  
  <p>It makes confused and uncomfortable, does anyone know why it is like that?</p>