Add bgen support

[evagradovich]

 Overview

This PR:

• Adds support for accepting .bgen files + accompanying .sample file as input
• Updates --vcfs_list to genotype_files_list with a new parameter - genotype_format with current options being vcf and bgen.
• New --bgen_sample_file to accept accompanying .sample file.
• New bgen2plink step that performs bgen-> plink conversion and subsets to samples present in pheno_data file.
• Small modification to change lambda to greek letter representation in QQ plot
• Updates docs/usage_and_parameters.md with new/updated params

Test

Lifebit CloudOS (Internal Production workspace)

https://cloudos.lifebit.ai/app/jobs/619b837afb26cf01dcee30de

[evagradovich]

https://cloudos.lifebit.ai/app/jobs/619ca920402cb601dde17c31

Small test with .bgen files finishes successfully in Lifebit Internal Production but fails with bigger dataset with memory allocation errors. Subsequent PR will involve memory optimization in light of GWAS benchmarks performed and will address issue https://github.com/lifebit-ai/gwas/issues/126.