Better contextmenu support for Tree

git-svn-id: https://primefaces.googlecode.com/svn/primefaces/trunk@10155 5a70e874-a5cb-11dd-8af2-493fb0bb9f7c
#6231

git-svn-id: https://primefaces.googlecode.com/svn/primefaces/trunk@10156 5a70e874-a5cb-11dd-8af2-493fb0bb9f7c
Merge branch 'master' into 4.0.x