Initial support for mcmc.list objects.

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/r2mlwin@288 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
Don't warn about multiple chains if mcmc.list only contains one element, and update trace plot axis label as the scale is now actual iteration numbers.

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/r2mlwin@289 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
Correct variable name.

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/r2mlwin@290 edb9625f-4e0d-4859-8d74-9fd3b1da38cb