major changes in order to subsample bam

src/modules/statistical_analysis/script/glm_stat.py

src/modules/statistical_analysis/script/sample_reads.py

src/modules/statistical_analysis/script/variant_counts.py

...odules/statistical_analysis/script/variant_frequencies.py

src/pipelines/nf_modules/analysis.nf

src/pipelines/nf_modules/picard.nf

src/pipelines/nf_modules/samtools.nf

src/pipelines/variant_calling.nf