Provide access in the landing page editor to all field definitions stored on a Landing Page content type

As of the time of this specification (eZ Platform EE version 1.10),

• The Landing Page management function is designed to work using the default LandingPage content type provided with eZPEE.
• The LandingPage content type is based on the LandingPage field type definition which is used to store the landing page structure and content.
• The other fields are not really used by editors simply and can not be edited from the landing page.
• The system is not designed to allow to change (add or delete) field definitions to the Landing Page content type (though it is possible, it is not usable).
• The system is not designed to allow to create different content types using the LandingPage field type.

This is limiting the flexibility offered by Studio.
With this evolution of the landing page feature, users

• Will be able to change the field definitions of the Landing Page Field type (add, remove field definitions as long as they don’t change the LandingPage field definition) so that users can simply access them.
• Will not be able to create new content type with the LandingPageFieldType to use them with the landing page editor.