[Feature Request] Make the raw data available on CsvMappingResult

[attilah]

I had to filter large CSV files without touching the input, so I had to have access to the input raw data per line during my processing core. I solved it by adding a RowData property to CsvMappingResult class and populate it during parsing.

It enabled me to use a custom mapper and do all the filtering needs on the parsed properties of the class, but if the filter returned true I was able to write out the original line into the output folder, making sure that escaping, etc would be preserved.