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
    }
}
```
Nit: Non-functional change. Change to "this.array" is fine.