Add BFC reading capabilities

This branch adds support for BFC files produced by LabSphere's BFC-450 spectrophotometer (#7 (closed)).

Having no official datasheet, this is based on retro engineering the file format from https://www.rit.edu/cos/colorscience/re_sgonzalez.php dataset.

EDIT: Now the link of the database is broken, not sure how you still can download the original files except from our private repository. Here is the archived webpage linked above: https://web.archive.org/web/20191018071813/https://www.rit.edu/cos/colorscience/re_sgonzalez.php