Return list of RawExtrensicMetadata instead of tuple

Currently map_row returns a complex tuple, that damages code readability, so instead of returning complex tuple it should return a named class RawExtrensicMetadata.

Add different fields like file, format in map_row, map_scancode, map_clearlydefined, map_licensee that are required to map previous tuple data with RawExtrensicMetadata. Add docstrings and tests.

Signed-off-by: Tushar Goel <tushar.goel.dav@gmail.com>