Fix default view for workflow view tabs

On the "workflow" view (available by cllicking on the "worflow" main tab, disabled byb default), tabs are using category "WORKFLOW_DASHBOARD" which is bound by default to action type "rest_document_link".

This action type does not use the right view for this tab: it'll use "view_documents" by default instead of "view_workflow", showing the wrong view when clicking on tabs.

This can be fixed by adding the following to the action configuration:

      <properties>
        <property name="view">view_workflow</property>
      </properties>

Let's define a distinct action type with this view by default (as it's been done for admin and home tabs) and bind the "WORKFLOW_DASHBOARD" category to this type instead.