add colMedians() {and rowMedians()} and *use* it

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/robustbase@670 694ef91d-65df-0310-b7bb-92e67a308ead
proper documentation for r6pack()

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/robustbase@671 694ef91d-65df-0310-b7bb-92e67a308ead
new colMedians(): part 2

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/robustbase@672 694ef91d-65df-0310-b7bb-92e67a308ead
 "Biweight on a Stick" 

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/robustbase@673 694ef91d-65df-0310-b7bb-92e67a308ead