Faster Python unittest

* User must install Paddle python package before unittest.
* Or use docker to build Paddle

ClangFormat for proto and cuda

Simplify CrossMapNormalOpTest and BlockExpandOpTest.

use isclose instead of assert_almost_equal

Merge branch 'clang-format' of https://github.com/gangliao/Paddle; branch 'develop' of https://github.com/PaddlePaddle/Paddle into clang-format

Reformat paddle/operators/* strictly following Google Style Guide

Make ci pass

Make test_CompareSparse eat less memory and faster.

Add explicit to some constructors

Re-structure source code of type Attribute

SKip cpplint if source is not changed.

Simplify test_matrixCompare

Move constants from framework::OperatorBase to framework::

convert dataset into recordio format

Enforce add more helpers