AstrobioMike/GToTree: GToTree v1.6.20

requiring and using muscle5 now thanks to note from @jianshu93 (https://github.com/AstrobioMike/GToTree/issues/48) using super5 algorithm by default if working with greater than 1,000 genomes, this can be prevented by providing the -X flag added options to gtt-get-accessions-from-GTDB to enable avoiding automatic GTDB database version check, and to store it in the current working directory if wanted (rather than the system variable ${GTDB_dir} setup during conda installation), thanks to feedback from @felixeye (https://github.com/AstrobioMike/GToTree/issues/45