Accommodate for scipy.interpolate.interp1d deprecation

[HannoSpreeuw]

The scipy.interpolate.interp1d class is instantiated twice in ìmage.Image.Data.interpolate.

However, the scipy.interpolate.interp1d documentation mentions that this class is considered legacy code:

This class is considered legacy and will no longer receive updates.
This could also mean it will be removed in future SciPy versions.
For a guide to the intended replacements for interp1d see 1-D interpolation.

i.e. at some point in time replacing this class instantiation with the numpy.interp routine may become necessary.