Thread Safe implementations of Boruvka, Prim & Kruskal algorithm

[sidml]

This can be nice issue for beginners.
For reference, existing Thread safe implementations are here. Similar pattern can be used for adding thread Safe implementations of Boruvka, Prim & Kruskal algorithm.

[ZigRazor]

No more applicable, the thread safeness of the functions will be reviewed in a second moment of the project