[FEATURE] Deferred execution

[KonStg]

Is your feature request related to a problem? Please describe.
The library almost entirely uses immediate execution.
This is inconvenient for use in linq-expressions, in which case most of the computation is wasted.

Describe the solution you'd like
Some typical functions with yield return. For example breadth and depth traversal, ancestor and siblings traversal and so on

Describe alternatives you've considered
For now I implement these functions myself