Copy mappy python interface for drop-in compatibility

[alexomics]

minimap2 already has a python interface, mappy we should aim to re-implement that API so that - in the first instance - this can function as a drop-in replacement.

For this we need:

• [ ] Same Aligner args
  • [ ] Take fn_idx_in as (MMI)
  • [ ] Take fn_idx_in as (FA)
  • [ ] Write to fn_idx_out (FA -> MMI)
• [ ] Same Aligner.map args
• [ ] Aligner.seq_names to work
• [ ] Aligner.seq to have the same behaviour
  • [ ] Return None on error rather than raise
• [ ] Same Alignment structure with attributes

Maybes:

• [ ] Misc functions:
  • [ ] fastx_read(fn, read_comment=False)
  • [ ] revcomp(seq)