Implement universal & complete set of mutations

[gkirgizov]

Current set of mutations (that came from FEDOT) is aimed at finding short trees and dags. Example of arbitrary graph search shows that these mutations are not sufficient for other use cases.

Based on this observation, the task here is to find a new, complete and universal set of mutations, that would enable effective search of different kinds of graph structures. Complete and universal means that such mutation set should be sufficient for any target graphs.

I see following steps:

• Review literature on used Mutation & Crossover operators for graphs #59
• Design complete set of mutations
• Experiment with it based on graph & tree search examples

Experiment cases must achieve optimization objective only with provided mutations (no crossover).

Possibly issue #38 would help in experiments.