[pyclustering.utils.metric] Categorical data for Gower distance

[annoviko]

Introduction There is request to support categorical data for Gower distance, like in following article:

• https://towardsdatascience.com/clustering-on-mixed-type-data-8bbd0a2569c3

Description It is not a big deal to support in python part of the library. But it is required well design solution for C++ part without any performance degradation.