Extend HMI:JsonTable, create Edit CSV POU, create example, add some doc (#41)
* Extend Jsontable widget, create Edit CSV POU, create example for both
* Add doc for HMI:Image and HMI:JsonTable
* Expand example to include HMI:Image
PLC variables and local variables==================================PLC variables start with ``/``------------------------------Local Page variables start with ``.``-------------------------------------Local HMI variables-------------------