Quick upload factory: also reindex dexterity types.

The quick upload factory currently executes `processForm` (from Archetypes) on newly created file objects.
When creating dexterity types (such as `ftw.mail`), `processForm` is executed on the acquision parent, since dexterity has no `processForm`.

This PR changes to this behavior to check whether we have `processForm` (AT) and fall back to a direct `reindexObject` when it is missing (DX).

@maethu can you take a look at this one?