Added taxonomy_distance() for calculating pairwise
taxonomic distances between OTUs from a taxonomy table.
Added support for filtering taxonomy assignments by confidence
scores through a new confidence argument in
taxonomy_tree() and
taxonomy_distance().
Extended vs_cluster_unoise() and
vs_cluster_size() with new arguments for controlling output
from clustering output: clusters and uc. The
uc argument was also added to
vs_usearch_global().
Added a verbose argument to functions that print progress messages or other information to the console.
Updated vs_optimize_truncee_rate() and
vs_optimize_truncqual() with an option to randomly sample
10,000 sequences when the input contains more than 10,000 sequences,
thereby reducing computation time.