* Python trainer API and demo

* Adding missing PaddleAPIPrivate.h

* Adding api_train.sh

* More comments

* Bump up patch version to 0b3

* Replace DataProviderWrapperConverter with DataProviderConverter in all
demo prediction scripts.

* Minor refinement of swig_py_paddle.rst to keep consistency with the
English version.

ISSUE=4586495

git-svn-id: https://svn.baidu.com/idl/trunk/paddle@1408 1ad973e4-5ce8-4261-8a94-b56d1f490c56