erp5_crm: display standard preview on Mail Message only if internet_message_post_module isn't installed

To prevent race-condition in a multi-node environement (ie: 2 activity nodes load the afterAllowExport activities for 2 Posts having the same reference)

The attachment field now uses the property aggregate_document_title of Event.

erp5_interface_post: interface_post_workflow prevents having several versions of the same post in the exportable queue

It will be used to differenciate attachments from Mime Post.

erp5_interface_post contains ***_post_modules, which purposes are to track posts that go out and in ERP5, without any processing.

erp5_pdm: use preferred category child item list method in my_variation_category_list field library.

Python script needs to be recompiled when they comes from a change of
class. This was done when business template was installing scripts, but
not when automatic migration from old catalog to new catalog was done.
So make sure to call _compile directly in changeObjectClass to make sure
Python Scripts would always work after a change of class.

Replace the airplane icon by a search button if not value is set on the field.
This make it more usable on mobile, where it's easier to browse than typing text.