add scg3 PRESEQ compatibility
add scg3 PRESEQ compatibility

also switch from rendering pdf plots to png ones for compatibility
kundajelab/atac_dnase_pipelines,kundajelab/atac_dnase_pipelines,kundajelab/atac_dnase_pipelines,kundajelab/atac_dnase_pipelines,kundajelab/atac_dnase_pipelines