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

Using Groups (svg:g)
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Nesting widgets
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Side effects of optimization
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Detachable pages
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Discardable elements
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