and change the size of test to make unit test faster
refine comment and log of mkldnnlayer

and add branch net comparing with cpu result

By shell command

```bash
sed -i 's#ifdef PADDLE_ONLY_CPU#ifndef PADDLE_WITH_GPU#g' `find ./paddle/ -name '*.h' -o -name '*.cc' -o -name '*.cpp' -o -name '*.c' -o -name '*.cu'`
sed -i 's#ifndef PADDLE_ONLY_CPU#ifdef PADDLE_WITH_GPU#g' `find ./paddle/ -name '*.h' -o -name '*.cc' -o -name '*.cpp' -o -name '*.c' -o -name '*.cu'`
```

* golang pserver optimizer config for user

* update

* update

* update

* update

* update by comments

* fix errors

* fix errors

* default learning rate, temperary fix

* update

* using etcd as fault tolerant training

* update

* workable version, ft not tested

* small fix

* update

* remove TODO

Use CHECK instead of PCHECK, because PCHECK is used for errno.

Fix #2567

1. v2.layer.parse_network does not correctly handle the generation output.
2. GatherAgentLayer does not correctly handle generation output when batch_size > 1
3. Fix CustomStackTrace for rnn group

No longer need to use SubsequenceInput. The framework will detect.