Fix the bug between nvcc and boost

* Should always use `dynload::` for cuda function.
* Fix cublas.h without DSO load.

turn off with_mklml and with_mkldnn to fix ImportError of libmklml_intel.so

Fix #3386

 tensor slight improve

fix test_KmaxSeqScore for only CPU compile.

gather function only

Random op

A better error message for gradient checker

Remove unnecessary C++ operator test

They are tested in Python

* Give which parameter, which element are wrong. And what max_diff is.

Make const variables in operator.h fit google style

Use ostream << operator to get to_string

* No POD instance is forbidden in global scope.

See
https://google.github.io/styleguide/cppguide.html#Static_and_Global_Variables

Merge pull request #3334 from reyoung/feature/ignore_some_files_which_will_generated_while_compiling

Ignore compile generated files for git

* Make `PADDLE_ENFORCE_EQ` supports custom class, like DDim

* merge InferShapeContext and OperatorContext

* OperatorBase& instead of OperatorBase*

Implement trainer init parameters election with etcd