refactored parent fallback handling

git-svn-id: http://primefaces.googlecode.com/svn/primefaces/trunk@10004 5a70e874-a5cb-11dd-8af2-493fb0bb9f7c
Remove descendants of a checkbox tree.

git-svn-id: http://primefaces.googlecode.com/svn/primefaces/trunk@10005 5a70e874-a5cb-11dd-8af2-493fb0bb9f7c