Dynamic column support

git-svn-id: http://primefaces.googlecode.com/svn/primefaces/trunk@10206 5a70e874-a5cb-11dd-8af2-493fb0bb9f7c
MultiSort support

git-svn-id: http://primefaces.googlecode.com/svn/primefaces/trunk@10207 5a70e874-a5cb-11dd-8af2-493fb0bb9f7c