[C/C++ pyclustering] Forbid to use cluster_data

[annoviko]

Introduction
Current interface may confuse because cluster_data might be used instead of concrete type (such as dbscan_data, fcm_data, etc.). As a result segmentation fault occurs. The cluster_data shouldn't be accepted by algorithms to avoid this situation, concrete implementation should be used instead. If there is no concrete implementation than alias must be created.

Description

• Update algorithm interface in order to use concrete type of data instead of cluster_data.
• Update unit-tests.
• Look for possibilities to forbid allocation of cluster_data, for example, to make it pure abstract class with partial implementation.

Links
There is an issue that indicates problem of current interface: #576 .