Move action constants to separate class
Extend context menu with add options.

It includes:
 * Create new Actions
 * Extend context menu
 * Extend EditPolicies to be able answer to request
Make selection visible using editPolicy
Handle validator attach and detach
Fix attaching validator when ValidationModel is empty
Make wizard page name constants public
Synchronize validators in new scenario wizard.

Validators can be managed in different pages in the wizard so changes
made in one section are now visible in the other one.
Fix synchronising in last commit

* It does worked only when user adds new message but not for edit