added editDataset.Rd. John

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/rcmdr@563 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
updated .pot file for data set editor; added editDataset.threshold Rcmdr option. John

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/rcmdr@564 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
fixed bug when new data set cancelled. John

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/rcmdr@565 edb9625f-4e0d-4859-8d74-9fd3b1da38cb