that other things named browser_id_manager can be created in subfolders.

Wrap transient data objects only in session data manager upon return.
Previously, they had been wrapped also in session data container.

Took out clever traversal error logging code in fear that it would
bloat the ZODB.

Added SessionDataManagerErr and BrowserIdManagerErr to API docs and
made them importable within a PythonScript.

Extended test suite with request-autopopulate tests.