Add HiveDecimal & HiveVarchar support in unwrapping data

might be a better way to write this:
```scala
    case hvoi: HiveVarcharObjectInspector =>
      if (data == null) null else hvoi.getPrimitiveJavaObject(data).getValue
    case hdoi: HiveDecimalObjectInspector =>
      if (data == null) null else BigDecimal(hdoi.getPrimitiveJavaObject(data).bigDecimalValue())
```