Contextmenu improvements

git-svn-id: https://primefaces.googlecode.com/svn/primefaces/trunk@10157 5a70e874-a5cb-11dd-8af2-493fb0bb9f7c
Fixed checkbox handling

git-svn-id: https://primefaces.googlecode.com/svn/primefaces/trunk@10158 5a70e874-a5cb-11dd-8af2-493fb0bb9f7c
Merge branch 'master' (early part) into 4.0.x
Tagged 4.0.1-UR (Unofficial Release).
Next maintenance iteration for 4.0.x