[x] options for each overlay dataset: (1) label on/off, (2) color selection (make consistent with color selection in Basic Plots), and maybe (3) shape selection
[x] add/modify get_snp_list, get_gene_list, get_gwas_list functions to allow multiple input lists (as separate columns). Return df with additional listName column (so listName can be labeled in volcano plot)
[x] GWAS catalog: allow selection of multiple traits
[x] order: InWeb, GWAS catalog, SNP, gene
[x] download buttons for: overlaid volcano plot, summary table of overlaid genes (and which list they came from) + relevant overlap enrichment statistics
Basic Plots
Integrated Plots