public String getPropName(){
      return this.propName;
    }
Enum container for all avro table properties.
If introducing a new avro-specific table property,
add it here. Putting them in an enum rather than separate strings
allows them to be programmatically grouped and referenced together.
serde/src/java/org/apache/hadoop/hive/serde2/avro/AvroSerdeUtils.java