Merge branch 'dev'

update some docu/comments

update changelog for Version 1.2.3

update changelog for version 1.2.2

update changelog

Update README.md

update

Disable xfce polkit

fix no connection via noVNC: fix the version of noVNC to the latest w…

…orking version via the fork https://github.com/ConSol/noVNC/releases/tag/consol_1.0.0

fix centos version to 7.2.1511