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

* add lod_tensor util and modify pybind

* refind pybind LoDTensor API and modify LoDTensor and DataFeeder test

* fix test error

* fix detection map op test

* fix reorder_lod_tensor test

* fix seq_concat_op

* fix chunk evel op test

* fix target assign op

* fix warp ctc op

* address comments step 1: reverse reset_lod op

* step 2: modify op test

* add warning message

* remove has_valid_lod

* add back has_valid_lod

* address comments

* add exception catching trial

* enable docstring checker and fix comments

* update

* update by comments

* fix build

* fix develop build issue

* fix google style

* cpplint check only fluid

* Add cpplint_pre_commit.hook

* Update hook

* Disable dropout_op_test.cc

* Remove cpplint.py but requires users to install their version

* fix cpplint error