Fix invalid paddle executable file path with pip install  

Otherwise the production image generation will fail due to deb not
found, or executable built from Go not found.

* remove external_project_dependencies for proto/CMakeLists.txt

Fix C-API Compilation Error

* put everything in paddle wheel

* update

* update

* fix unitest

* with platform specs

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

* Do not use `virtualenv` in Docker
* Split unittest into many target, make them parallel

and disable both when build doc and MacOS

* using etcd as fault tolerant training

* update

* workable version, ft not tested

* small fix

* update

* remove TODO

The newest developing image was push to dockerhub, named xreki/paddle-android:dev.