programmatically submitting form: drupal_execute should return useful data.

Issue Summary

When programmatically submitting a form, drupal_execute is returning a string which is the redirect path (e.g. admin/content/taxonomy after submitting a term).
The problem is that often we want the ID of whatever has been submitted (nid, tid, fid, etc). We miss the equivalent of mysql_insert_id().

In the case of a node, we can get the nid from the returned path (node/nid), but for many other forms, we have to go on very roundabout ways to get the ID (i.e. query the DB for the term we inserted, hoping there is no identical terms, or two forums with the same name, etc..)