add inverted y-scaling for accuracy cell + performance metric curves

[gfrogat]

the current implementation of the y-scaling lets a user focus on the bottom region of the charts, but as the accuracy cell is handled identically to all the other cells we actually de-focus the accuracy curves.

I suggest we add an inverted y-scaling to the accuracy cell and the performance metric cells --> when "zooming in" we focus on the upper region instead of the bottom