Add new "content views" feature in studio

In studio, we should be able to define content views in a new feature (new item on the tree, like virtual navigation for instance)

Edition screen:

---> Provide form layout with query operator
The way it works today for advanced search configuration should be kept.

---> Configure an action filter
We already have such interfaces.

---> Provide the NXQL query, with dynamic access to the context
It is not clear to me what context we would have access to, although this is very important and we need to define it accurately.

---> Design the resultset screen

• to design a result set, the user should drop fields in a one-line table.
• there would be built-in static widgets, such as live edit link, download link, pdf transfo, path, ...
• for a given widget, it is possible to configure whether it is sortable or not (the default sort is given in the query configuration, not here)