+- added exceptions module, all raised exceptions (except for some
+KeyError/AttributeError exceptions) descend from these classes.
- fix to date types with MySQL, returned timedelta converted to datetime.time
-- begin/commit now returns a transactional object, to more clearly indicate
+- two-phase objectstore.commit operations (i.e. begin/commit) now return a
+transactional object (SessionTrans), to more clearly indicate transaction boundaries.
- Index object with create/drop support added to schema
- fix to postgres, where it will explicitly pre-execute a PassiveDefault on a table
if it is a primary key column, pursuant to the ongoing "we cant get inserted rows