Vignettes changed to use knitr and section added to xtableGallery.Rnw to illustrate the use of xalign, xdigits and xdisplay

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/xtable@54 edb9625f-4e0d-4859-8d74-9fd3b1da38cb