* Added `delta_u` and `delta_v` properties to Surface classes. This change allows different sampling in u- and v-directions
* Fixed some bugs related to `sample_size` property
* Replaced `delta` with `sample_size` in Multi classes. `sample_size` property directly corresponds to `num` argument in [numpy.linspace](https://docs.scipy.org/doc/numpy/reference/generated/numpy.linspace.html) function.
These changes may cause a small API break in your existing code, especially if you are visualizing using the `geomdl.visualization.VisMPL` component.
Please see the examples repository and check any example for the updated usage scenarios.