The Spark verifier of a presenter definition

It runs one time for each module that uses Expresso.Presenter.Dsl, when the module compiles. It refuses these errors:

• The option state does not hold exactly the fields of Expresso.Presenter.Definition, or a value has the wrong type.
• The option sync, the option reset or the option match of a mode names an unknown field. The option sync or the option reset names index.
• Two modes have the same name.
• A command is not a command of Expresso.Presenter.Definition, or it gives a field a value of the wrong type.
• A mode with the option any has bindings.
• One event has two bindings in one mode. The list of keys would then show two functions for the event.
• The event :element is in a mode without the option element.
• A projection names an unknown field, or an attribute or a property with a wrong name. Expresso.Presenter.Projection describes the projections. An attribute with flag: true needs a field that is true or false, and a mark needs a field that holds a number.

The script in the browser reads the same fields and commands. Without the verifier, the script finds such an error only when the presenter uses the document.