[GSoC] Container proposals by Ishan and Christian

[bearophile]

Ishan Thilina:

> I looked at few things( such as Skip list, Binary decision tree, Trie, rope) that
> was listed in that page. Yes, things such as Skip list and Binary decision tree
> looks interesting. But to be honest I have never heard about those data structures
> before.

Some data structures useful for Phobos:
- a graph;
- a hash set;
- A deque made with a dynamic array of fixed sized arrays;
- a Union-Find (not too much hard);
- a Bloom filter (easy with the already present bit arrays);
- a dawg;
- a simple trie;
- a BK-tree;
- a bidirectional associative array;
- a parallelizable immutable finger tree.

Bye,
bearophile