[ccore.clst.silhouette] CCORE Silhouette implementation

[annoviko]

Introduction
Silhouette uses C/C++ implementation of K-Means, but also performs analysis of obtained results where Python implementation is used. In the case of big data and search range, a lot of resources are spent to transfer results from and to CCORE and it increases the complexity of the algorithm by

O(n) * 2 * (kmax - kmin);

Therefore pure C/C++ implementation of the algorithm is required to avoid useless data passing (reduce complexity).

Description
Following tasks should be done in the scope of the issue:

• Silhouette and interface to it should be implemented using C/C++ (namespace ccore.clst, class silhouette).
• Unit and integration tests for the implementation are required.