Create the toolbox + data input - docs and tasks
Goal: provide a toolbox, and data input widgets from the toolbox in the context of doc and tasks layouts.
=> in this we'll need to make sure we cover
- the binding management, because it may be almost useless otherwise (if you can't easily select the field but only the ui element, it makes it even more complicated than as of today)
- which properties to show in the popup / in the properties tab (this work should help with support around custom elements, because we'll see what annotations we need). Typically in the popup we could start with the required properties if there are any (otherwise we can't generate the element...) and the label.