text: Title: Replace Stacked Barchart with Group Bar chart with shared axes
  Body: Currently the stacked bar chart is used when 2 categorical variables and 1 quantitative variable are specified. This works when the aggregate function is sum, but the chart is not very interpretable when another aggregate type is used. 
  
  **Current Chart used**
  ![pasted image 0](https://user-images.githubusercontent.com/25440626/94630094-8d4f1280-0279-11eb-8346-b1200562f266.png)
  
  **Alternatives**
  ![pasted image 0 (1)](https://user-images.githubusercontent.com/25440626/94630471-bae88b80-027a-11eb-89b1-3e7668d50b03.png)
  
  ![pasted image 0 (2)](https://user-images.githubusercontent.com/25440626/94630473-bde37c00-027a-11eb-95a2-ba9394d12cd1.png)
  
  While the heatmap chart is the more space efficient alternative, it is a bit harder to interpret compared to the grouped bar chart. We will implement the grouped bar chart, but will need to modify the grouped bar chart to share axes, similar to matplotlib's [shared axes grouped bar chart](https://matplotlib.org/3.1.1/gallery/lines_bars_and_markers/barchart.html).
  Again for compactness reasons, we may only chose to apply this when the color attribute has less than 3 distinct values.