`Tester` PySpark data support

[xandaau]

This issue was created to track the development of PySpark support for methods of the Tester class.

The current functionality of the Tester does not support any operations on spark data. However, this is very important for big data scenarios, and given that we already had PySpark support for Designer and Tester, it seems, that such Tester enhancement is vital for us.

In my opinion we should focus on these two points:

1. Developing a PySpark implementation of stat criteria (is essential for Designer and others) PySpark statistical criteria implementation  #19
2. Optimizing the execution speed of Tester methods