This is part of big move of v2 codes to legacy sub dir.

* fix develop build issue

* fix google style

* cpplint check only fluid

Remove the pserver, trainer, evaluators and some useless gradientmachines when compile mobile inference library.

* fix remote large update core

* wip

* working version

* fix style check

* fix style check

* update style check

to create a gradient machine for inference using merged model with parameters
which is genearted by `paddle merge_model`.

Please use `override` not `virtual` in sub-classes.
`override` can check if there is a method in `parent` while compiling.

Make the evaluators inside a recurrent goup true evaluator, meaning that their evaluation results are incorporated into the whole evaluator result.

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

* also remove unused getValueStr

* Different Type compare.
* ostream << should pass a const object.
* remove always true checks.

* Different Type compare.
* ostream << should pass a const object.
* remove always true checks.

* follow comments to fix bugs

* Make layer stack trace shows ThreadId, Forward or Backward.

Change-Id: Iba1477adb8c9115c3a67ff2959bb5c878ca706c7

* Make layer stack trace shows ThreadId, Forward or Backward.

Change-Id: Iba1477adb8c9115c3a67ff2959bb5c878ca706c7

ISSUE=4586495

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