aligned functionality for rasch/rs/pc further, in particular adding
itempar() and predict() methods

enhanced/updated the corresponding documentation to be in sync with the
new interface based on partykit and psychotools-ng

fixed node_profileplot for infinite parameters -> node_regionplot still
returns bogus results in this case

consistency touch-ups in documentation



git-svn-id: svn://svn.r-forge.r-project.org/svnroot/prefmod@246 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
touch-ups

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/prefmod@247 edb9625f-4e0d-4859-8d74-9fd3b1da38cb