avoid SortFeature instantation - it's already available

git-svn-id: http://primefaces.googlecode.com/svn/primefaces/trunk@11111 5a70e874-a5cb-11dd-8af2-493fb0bb9f7c
#6854

git-svn-id: http://primefaces.googlecode.com/svn/primefaces/trunk@11112 5a70e874-a5cb-11dd-8af2-493fb0bb9f7c
#6856

git-svn-id: http://primefaces.googlecode.com/svn/primefaces/trunk@11113 5a70e874-a5cb-11dd-8af2-493fb0bb9f7c
Set 1 as default columns number when undefined

git-svn-id: http://primefaces.googlecode.com/svn/primefaces/trunk@11114 5a70e874-a5cb-11dd-8af2-493fb0bb9f7c