Exec Dashboards: Add sparkline to the metrics comparative table

Overview

Once the Exec Dashboards MVC will be completed, we need to add sparklines to help our users quickly understand the metrics performance over time.

Problem to solve

User experience goal

1. Quickly identify patterns in metrics trends (seasonal changes or other cycles).
2. Quickly compare metrics improvement over time.

Proposal

1. Add sparklines line charts for each metrics.
2. The sparkline will display the metrics value trends (not change rate %).
3. The sparkline will display the past six months data, aggregated monthly.
4. Data order from left to right.
5. Y-Axis start at 0.
6. To improve performance please consider lazy loading of the sparklines.
7. Out of scope for this issue - highlight the sparklines maximum and minimum values in a different color.