Add pretty printers for common biological file formats

[kMutagene]

As analyzing biological data with BioFSharp involves a lot of scripting, optional pretty printers help a lot when looking at results directly in the fsi window. This should be especially easy to add for parsing libraries that can already write the correct file format. A basic pretty printer for biocollections is already impelemented. Here are some formats from the top of my head, feel free to add more

• [x] BioCollections (BioList,BioArray,BioSeq)
• [x] Clustal
• [x] GFF
• [ ] FastA/Q
• [ ] GeneBank
• [ ] Alignments

[kMutagene]

GFF added via eaaa59fbd382721e75fbb9c6558b0ba2ff6afb00