More tree dragdrop work, added multi drag feature

git-svn-id: http://primefaces.googlecode.com/svn/primefaces/trunk@9262 5a70e874-a5cb-11dd-8af2-493fb0bb9f7c
#5655

git-svn-id: http://primefaces.googlecode.com/svn/primefaces/trunk@9263 5a70e874-a5cb-11dd-8af2-493fb0bb9f7c
#5651

git-svn-id: http://primefaces.googlecode.com/svn/primefaces/trunk@9264 5a70e874-a5cb-11dd-8af2-493fb0bb9f7c