Fix for unique reference ids under robust counting with multiple partitions (issue 747).

git-svn-id: http://beast-mcmc.googlecode.com/svn@6531 ca793f91-a31e-0410-b540-2769d408b6a1
Updated release notes

git-svn-id: http://beast-mcmc.googlecode.com/svn@6532 ca793f91-a31e-0410-b540-2769d408b6a1
Add parser option to randomize initial discretized branch rate categories.

git-svn-id: http://beast-mcmc.googlecode.com/svn@6533 ca793f91-a31e-0410-b540-2769d408b6a1