This commit introduces entropy-based filtering for k-mers to remove low-complexity sequences. It adds:
- New KmerEntropy and KmerEntropyFilter functions in pkg/obikmer/entropy.go for computing and filtering k-mer entropy
- Integration of entropy filtering in the k-mer set builder (pkg/obikmer/kmer_set_builder.go)
- A new 'filter' command in obik tool (pkg/obitools/obik/filter.go) to apply entropy filtering on existing indices
- CLI options for configuring entropy filtering during index building and filtering
The entropy filter helps improve the quality of k-mer sets by removing repetitive sequences that may interfere with downstream analyses.
