Better handling of underflowing denominators.

git-svn-id: http://beast-mcmc.googlecode.com/svn@6559 ca793f91-a31e-0410-b540-2769d408b6a1
Cleaning

git-svn-id: http://beast-mcmc.googlecode.com/svn@6560 ca793f91-a31e-0410-b540-2769d408b6a1
git-svn-id: http://beast-mcmc.googlecode.com/svn@6561 ca793f91-a31e-0410-b540-2769d408b6a1
Experimental Parallel MCMC experiments.

git-svn-id: http://beast-mcmc.googlecode.com/svn@6562 ca793f91-a31e-0410-b540-2769d408b6a1