Introduce different line weights to separate between the smallest visible separator (steps) and single chart values (ticks). Calculate the amount of ticks per step using the available chart space.
fixes#7846
Use explizit number formatting instead of implicit type conversions when
rendering SVGs, to prevent a change of the locale from breaking the charts.
fixes#6585
Matthias Jentsch
Johannes Meyer
Eric Lippmann
Marius Hein
Jannis Moßhammer