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
Use floats as path coordinates in PieSlices, to
avoid that the start and ending position of the arc are at the exact same
position. This would cause buggy behavior, when displaying values like "99,999%".
refs #5863
Johannes Meyer
Matthias Jentsch
Eric Lippmann
Jannis Moßhammer
Marius Hein