Demo: Generative Adverserial Nets

Fix --job=test

When the define_py_data_sources2 has both train_list and test_list,
for job=test, the trainer will create both dataProvider_ and testDataProvider_.
But dataProvider_ is not used. This causes SIGSEGV at finishAsync() because asyncLoader_ is not created.

Change-Id: If579f715f80a70ebc795094792c3436bfa0f5746

refine build_docker_image.rst

Unify conv

Added a test in test_NetworkCompare to verify cudnn and exconv, fixed a bug in cudnn_conv in dealing with groups

remove build of doxyfile

Using ApproximatelyEquals for trainer config unittest.

fix style problem in doc_cn/introduction/index.rst

Release/v0.9.0

* Make float equal works well.
  * compare 0.01 and 0.009999999999 will return true.

Refine documentation in RELEASE.md

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