increased development version to 2.1-0 and re-included exams2blackboard()
in the development version



git-svn-id: svn://svn.r-forge.r-project.org/svnroot/exams@725 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
included header argument with custom Date/ID in exams2pdf() example of exams_skeleton()

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/exams@726 edb9625f-4e0d-4859-8d74-9fd3b1da38cb