- factored some fixes from trunk to lazyloader use_get, logging

- factored some fixes from trunk to lazyloader use_get, logging
- deferred inheritance loading: polymorphic mappers can be constructed *without*
a select_table argument.  inheriting mappers whose tables were not
represented in the initial load will issue a second SQL query immediately,
once per instance (i.e. not very efficient for large lists),
in order to load the remaining columns.