- fixed table comparison example in metadata.txt
- docstrings all over the place
- renamed mapper _getattrbycolumn/_setattrbycolumn to get_attr_by_column,set_attr_by_column
- removed frommapper parameter from populate_instance().  the two operations can be performed separately
- fix to examples/adjacencytree/byroot_tree.py to fire off lazy loaders upon load, to reduce query calling
- added get(), get_by(), load() to MapperExtension
- re-implemented ExtensionOption (called by extension() function)
- redid _ExtensionCarrier to function dynamically based on __getattribute__
- added logging to attributes package, indicating the execution of a lazy callable
- going to close [ticket:329]

    keyword argument to relation().  the old way still works but is
    deprecated [ticket:212]

- fix attribute unit test
- attributes have explicit flag for "mutable_scalars", propigated by ColumnProperty

test objects
- added copy_function, compare_function arguments to InstrumentedAttribute
- added MutableType mixin, copy_value/compare_values methods to TypeEngine,
PickleType
- ColumnProperty and DeferredProperty propigate the TypeEngine copy/compare
methods to the attribute instrumentation
- cleanup of UnitOfWork, removed unused methods
- UnitOfWork "dirty" list is calculated across the total collection of persistent
objects when called, no longer has register_dirty.
- attribute system can still report "modified" status fairly quickly, but does
extra work for InstrumentedAttributes that have detected a "mutable" type where
catching the __set__() event is not enough (i.e. PickleTypes)
- attribute tracking modified to be more intelligent about detecting
changes, particularly with mutable types.  TypeEngine objects now
take a greater role in defining how to compare two scalar instances,
including the addition of a MutableType mixin which is implemented by
PickleType.  unit-of-work now tracks the "dirty" list as an expression
of all persistent objects where the attribute manager detects changes.
The basic issue thats fixed is detecting changes on PickleType
objects, but also generalizes type handling and "modified" object
checking to be more complete and extensible.

- added "batch=True" flag to mapper; if False, save_obj
will fully save one object at a time including calls
to before_XXXX and after_XXXX