Implement layouts validation in document layout, content view layouts, advanced search and Step layouts

If on a widget dropped in a layout editor, a schema or a property is referenced but doesn't exist, the document, or the search feature, the content view, ... should be flaged as with one or more errors, as well as (ideally) the corresponding tab in the editor, and finally each of the erroneous widgets, with a message such as "property 'semper:happy' does not exist ".

Ideally,queries in content view definitions should also be parsed for schema:field names

We would also like to check if the widget chosen is consistent with the type of the property (both the fact of being multi-valued and the raw type).