Simplify the workflow initialization form

When initializing the workflow in a document, it is difficult for beginner users to understand how to fill in the given form (Publication page, Publication space, Workflow). While keeping the transparency (allowing users to modify the fields), it would help if the form fields would be prefilled and hidden by default. So, the form would have :

• The target data (Page and Location) prefilled with the current document data;
• The workflow value prefilled with the workflow matching the closest parent location (if any);
• By default, hidden prefilled fields;
• The option for the user to change the values of these fields.