Support for stream processing variable length records

@yruslan
I have large set of input files for processing. I wanted to take the stream processing approach. But, when i tried with the same options that i have successfully used for variable length records, like,
`
.option("generate_record_id", true)
.option("is_record_sequence", "true")
.option("is_rdw_big_endian", "true")
.option("variable_size_occurs", "true")
`
It was getting processed as FixedLength records.

Any thoughts or suggestions?