Add a tab for gene expression in form of violin plots. Multiple genes from a drop down can be visualized based on the selected cell type. From the same tab, these genes can be added to the current panel.
Add testing for feature above
Fix legend visibility when there are more than 15 factor levels for the selected cell type. Makes use of calculating the number of columns for visualizing the legend. Resolves #89
Add additional testing for changing UMAP and heat map options
Summary of proposed changes: