Replace bare SubversionException implemented in C with

Replace bare SubversionException implemented in C with
SubversionException written in Python, exposing the full chain of
svn_error_t objects.

* subversion/bindings/swig/python/svn/core.py
  (SubversionException): Add Exception class with apr_err, message,
    child, file, and line attributes, plus args attribute that is
    compatible with pre-1.5 bindings.

* subversion/bindings/swig/python/libsvn_swig_py/swigutil_py.c
  (SubversionException, svn_swig_py_exception_type,
   svn_swig_py_register_exception): Remove.
  (svn_swig_py_svn_exception): Turn svn_error_t chain into
    svn.core.SubversionException chain and raise that.

* subversion/bindings/swig/python/libsvn_swig_py/swigutil_py.h
  (svn_swig_py_exception_type, svn_swig_py_register_exception): Remove.

* subversion/bindings/swig/core.i
  Drop reference to svn_swig_py_exception_type.
  Don't register SubversionException here.

* subversion/bindings/swig/python/tests/client.py
* subversion/bindings/swig/python/tests/mergeinfo.py
* subversion/bindings/swig/python/tests/repository.py
* subversion/bindings/swig/python/tests/wc.py
  Import SubversionException from svn.core instead of libsvn.core.

git-svn-id: http://svn.collab.net/repos/svn/trunk@28226 612f8ebc-c883-4be0-9ee0-a4e9ef946e3a