Add 'zoom x' and 'zoom y' to grapher and regression

[jrkimber]

Hi,

Quite often, it is useful to zoom in on a graph only on the x-axis or y-axis, to see the shape of the graph in more detail, or to see a regression line better.

Currently, to do this, you have to go into 'axes' and change the range manually. It would be useful if there were buttons, or a combination of buttons to zoom in and out in only the x or y direction, in the same way that you can use '+' and '-' to zoom overall.

Thanks,
James