- update NEWS and advanced topics vignette

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/pomp@1012 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
- add 'values' method for 'probed.pomp' objects
- fix DESCRIPTION file

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/pomp@1013 edb9625f-4e0d-4859-8d74-9fd3b1da38cb