An implementation of Class based on skip-list.

Expected time complexity of deletion is O(1), while insertion still normally has logarithmic complexity.

The skip-list's nodes are implemented via fine-grained Linked List. In addition, RNG are distributed among capabilities which reduces contention.

Default maximum height of skip-list node is 16. Use explicit constructor in case the height needs to be changed.

Note: number of capabilities is not supposed to be changed during execution.