move ValidationError to C++
move TypedList validation error to C++

This removes the need to subclass TypedList from Python.  A Python
subclass is undesirable since the tp_as_mapping and tp_as_sequence slots
are overridden by type_new with slots which dispatch to the __getitem__
method call. This call is 3x slower than the builtin slot.
add errors.cpp to the build
change the build version to "dev"