Fixed checkbox tree selection issue

git-svn-id: http://primefaces.googlecode.com/svn/primefaces/trunk@11851 5a70e874-a5cb-11dd-8af2-493fb0bb9f7c
Refactor

git-svn-id: http://primefaces.googlecode.com/svn/primefaces/trunk@11853 5a70e874-a5cb-11dd-8af2-493fb0bb9f7c
Set expanded as false on collapse

git-svn-id: http://primefaces.googlecode.com/svn/primefaces/trunk@11854 5a70e874-a5cb-11dd-8af2-493fb0bb9f7c
Fixed #7453

git-svn-id: http://primefaces.googlecode.com/svn/primefaces/trunk@11855 5a70e874-a5cb-11dd-8af2-493fb0bb9f7c