mapseq v2.1 with updated reference 3.0

• Updated MAPref to v3.0 with new MAP OTU labels as used on the Microbe Atlas Project website (https://microbeatlas.org/)
• Updated NCBI taxonomy (Feb 2021)
• Added paired end analysis which automatically handles overlapping and non-overlapping paired end sequence mapping
• Added a sensitive mode for more accurate analysis needed in some applications
• Added -asvotutable option to generate a merged count table from several ASV count tables