note: v6 dropped empirical heuristics

remove uncertain old-vs-new note

note about old vs new classifier

simplify table: only ASHQ1 vs Q6_K

add comparison table

add Q6_K vs ASHQ1 comparison

license: apache-2.0 -> mit

v6: classifier overhaul, IQ tiers, has_imatrix safety, --allow-q3-or-lower

ASHQ1 v6: IQ tier spectrum, --allow-q3-or-lower, has_imatrix safety