set elephantbird compatible flag to get compatible schema and  value converter

1. renamed flag name to parquet.pig.elephantbird.compatible
2. getSchema in ParquetLoader where return converted schema, where boolean is converted to int
3. TupleConverter#newConverter will return a FieldIntegerConverter when flag is set. It means that if the underlying value is true, addBoolean method will add 1, otherwise it will add 0