Add bounding box/people detection to Swimlane

Based on the bounding boxes we could now add a new optional lane to the swimlane to indicate how many people are visible in the video (amount of bounding boxes). Might require some flattening of the count (if there's only 1 second another bounding bounding box, it's probably a glitch).

You will probably find a better way to implement it but here's what I roughly mean: