Add option to use ntLink for mapping step

[lcoombe]

• When mapping=ntLink is added to the tigmint-make command, use ntLink for mapping long reads to the draft assembly instead of minimap2
  • For this ntLink mapping approach, doesn't split the long reads into pseudo-linked reads
• Add option to use memusg for benchmarking the pipeline (if found in PATH)
• Bugfix in tigmint-cut
  • Could lead to distinct molecule extents being recognized as duplicates erroneously (More common to be seen when using ntLink mappings vs. minimap2)