implement checks for identifiability of functional effects; implement shrinkage penalty pss; each bl calls X_() function to compute all settings -> bkronecker.R of mboost can be used; for irregular response id has to be specified as formula ~id

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/fdboost@112 edb9625f-4e0d-4859-8d74-9fd3b1da38cb