Change name of `Scale::compute_autoscale()`

[sebjameswml]

Would like

Scale<float>::scale_for_range (0.0f, 10.0f);
morph::range<float> r1(0.0f, 10.0f);
Scale<float>::scale_for_range (r1);

[sebjameswml]

Can simply add these functions without removing compute_autoscale() for the time being.

[sebjameswml]

or maybe

Scale<float>::set_input_range (0.0f, 10.0f);
morph::range<float> r1(0.0f, 10.0f);
Scale<float>::set_input_range (r1);
Scale<float>::set_input_range (morph::range<float>(0.0f, 10.0f));