Converts measured metrics.patches into spatial raster objects.
In order to so, a patch coordinates needs to be measured (pxcor/pycor).
For each additional patch metric, a raster will be created using the
measured coordinates as x and y and the additional metric as z dimension.
In case of multiple measured metrics, a raster stack with one raster
for each metric will be reported.
In order to use this function, simulation results need to be attached to
the nl object first.