Percentage tick labels

**What can we do to make ScottPlot better?**
I'm trying to do a Scatter plott with percentages on both axes. It'd be great it ScottPlot supported conversion from "0.3184" to "31.8%" with a simple flag.

```cs
var plot = new ScottPlot.Plot();
...
plot.Ticks(percentages: true);
```

A more flexible, alternative solution of #297 might help in this case as well.