Add excluded_chunk_types to ChunkEvaluator

The chunks of types in excluded_chunk_types will not be counted in
ChunkEvaluator. This is useful for tasks such as SRL, in which chunks of
type V (verb) will not be taken into account in evaluation.

Add unittest to cover SgdThreadUpdater's enableBufType

fix typo: you -> we

fix dead links and refine tutorials/index

Fix RNN unittest bugs.

Added support for cudnn v6 and cuda 8.0

Clean BatchNorm Code.

add cluster_train_cn.md

refine data_sources.py and PyDataProvider2.py to make more readable

Add index_cn.md for test generation tutorial

fixed a bug for demo/gan caused by batchNormLayer

fix bug of 'shuf' and 'gshuf' in demo/recommendation/preprocess.sh

Remove redundant code

修正tutorial原文中的笔误

根据review结果修正一些翻译

* The DataProvider should be INCREF every time.

Hi paddle developers, In this tutorial, I guess it should be `We` rather than `You` according to context. Please check it, thanks.

Temp disable errored unittest