Enhance heatmap plotting

[genomics-kl]

• New function to filter out intersections of DE genes from bbcSE object. Usage: intersect_degs(bbc_obj, de_in=list(contrastA, contrastB, contrastC)). Can implement venn::venn or similar to do this easily.

• Add ability to filter columns by regex. Can just implement using grep.

• Option to plot either log normalized counts, their means or LFCs parsed from the contrasts stored in bbcSE.

• New function to extract the Ensembl IDs for specific gene sets from KEGG, Reactome etc