Ignored steps seem not to be treated correctly if axis does not start from zero

[grangoni]

If the lowest value of the axis is not zero, it seems that ignoredSteps are not treated correctly. I mean that ignored steps are not positioned correctly on the axis. There are precisely shifted by the axis origin value.

I managed to circumvent the issue by deducting the origin value of the axis from all ignored steps (from and to) but it seems not to be coherent with the other parameters of the widget.

There seems to be also another issue: when ignored steps start from the axis origin, it seems to be still possible to select that origin value on the left instead of ignoring all value from the left to the end of the first ignored step, including the (from value, on the extreme left).
I've not checked if the same happens on the extreme right yet.