make ff with limits (much!) more efficient: only write relevant parts of X-trajectories instead of the whole shebang into design matrices; improved pffrSim 

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/refund@161 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
fix coef for pcre with 1 FPC; minor doc fixes; ff-hist now actually works.

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/refund@162 edb9625f-4e0d-4859-8d74-9fd3b1da38cb