Add rgi/bwt

[vinisalazar]

Summary of changes:

• rgi/bwt: add draft
• rgi/bwt: editing input channel

cc @nickp60

[vinisalazar]

@nickp60 we might want to adjust the output channels a little bit, looks to me as though these are the main files:

test.allele_mapping_data.txt
test.artifacts_mapping_stats.txt
test.gene_mapping_data.txt
test.overall_mapping_stats.txt
test.reference_mapping_stats.txt

[vinisalazar]

@SPPearce thank you for the review, addressed your comments.

[nickp60]

@vinisalazar Thanks for doing all this! I agree with changing the output to specify those 5 outputs; that seems in line with the description in the docs

[vinisalazar]

@SPPearce could this be merged as is, and I can have a go at @nickp60's suggestion on a later PR (along with updates to rgi/main, perhaps)?