Backgammon Notation

[jamesdfrost]

Changes to use Backgammon standard narrative formats for human readable notation, as follows:

• Always show the numbering going from Bar->24->0->Off, irrespective of which player is moving.
• Show the start position followed by end position, instead of start position, number of moves. E.g. 24/22 10/8
• Show hits with an asterisk, e.g. 9/7*.
• Order the moves by highest number first, e.g. 22/7 10/8 not 10/8 22/7. Not an official requirement, but seems to be standard convention.
• Show duplicate moves as 10/8(2) instead of 10/8 10/8.
• Show moves on a single piece as 10/8/5 not 10/8 8/5
• Also introduced tests to check for the above scenarios.

Files changed - backgammon.cc, backgammon_test.cc and backgammon.txt (for the playthrough tests)

[lanctot]

Ok, @jamesdfrost , I've started to import it. Should go in on the next update.