Refactor into a function
Refactor to reduce code duplication parsing BLAST best hits
Refactor to preserve A record order & use less memory

NOTE: Slight difference to output from older version prior to
refactoring notices when have identical sequences present (e.g.
multiple copies of a short gene like a tRNA), where there is no
unambiguously define 'best' hit.

May wish to consider best-equal hits (which can happen with non-
identical sequences too)?