PARQUET-83 : Hive Query failed if the data type is array<string>

Changed the  Parquet-Avro array definition to the Hive understandable.
Now with this fix Avro schema definition is going to be converted to the following format as below.
```
{ "name" : "action", "type" : [ { "type" : "array", "items" : "string" }, "null" ] }
```
Schema definition after this fix:
```
optional group action {
    repeated group bag {
        optional binary array_element
    }
}
```
Which is the better option here either changing the ConversionPatterns class listType method
```
  public static GroupType listType(Repetition repetition, String alias, Type nestedType) {
    return listWrapper(
            repetition,
            alias,
            LIST,
            Types.repeatedGroup().addField(nestedType).named("bag")
    );
```
or modifying the list definition option only in the AvroSchemaConverter class and leaving ConversionPatterns.listType method unmodified.
```
      return ConversionPatterns.listType(repetition, fieldName,
              Types.repeatedGroup().addField(convertField("array_element", schema.getElementType(),
                      Type.Repetition.OPTIONAL)).named("bag"));
```
What do you feel is the better option?
ConversionPatterns is used across multiple parquet projects and this needs further changes in the list definitions wherever used in other parquet projects like parquet-pig and parquet-thrift classes.