Add Velocity Coefficient of variation

[Sebastiaan127001]

problem: QT can measure the velocity of a team from the last X sprints but there is no direct cause and effect relation to velocity and quality.

suggestion: in addition we could create a metric that measures the variance of the last X sprints. This will show the steadiness of the velocity and gives a better idea of how the team is planning

[Sebastiaan127001]

Moreover, a slowly increasing velocity (over >6 sprints) can also be in indicator of a team that is working more and more efficient.