Add Two-Way Astar

[dkastl]

Initially received as a patch there is now also a Github repository for the original "Two Way A-Star" algorithm": https://github.com/sroycode/tway

And there is also a fork of pgRouting, which contains the algorithm: https://github.com/sroycode/pgrouting

[woodbri]

Is this different from the bi-direction dijkstra and astar algorithms that are already part of 2.0?

[dkastl]

I don't know. But just see this ticket as a reminder. That'S why I added it to 2.1 Milestone, so don't need to think about now.

[cvvergara]

I was looking at the code of the link, @woodbri is correct, its the bidirectional A* as we know it in pgRouting.
On I will label pgr_bdAstar for version 2.5 on the rewrite, also have the same options for the heuristics mentioned here:
http://docs.pgrouting.org/2.4/en/src/astar/doc/astar.html#heuristic
I'll close this issue: as it is pgr_bdastar,
and open a new issue mentioning the rewrite expectations.