New graph for Tissue Dashboard
There is currently a statistic in the Tissue Dashboard for "Systems with multiple open events".
This statistic is usually empty.
In order to highlight systems with Tissue activity (e.g. events either open or closed), I propose
a new graph to the right of the above with the title "Systems with events during the past 30/60/90 days".
This graph would list the system name along the X-axis and the number of events created in the past
30/60/90 days on the Y-axis (i.e. stacked bar chart). On the 10 systems with the most events during
the past 90 days would be shown.