Allow clipping of population numbers if origin has far more wasps than elsewhere

[mountaindust]

In the early parts of the population model, all scale is broken and "hot spots" are invisible because the plot is scaling to the maximum population density at the origin. Instead, omit the origin when calculating the colormap norm and allow it to clip so that the structure of the spread becomes visible.

[mountaindust]

This will be fixed when popmodel is merged.