port dyload to platform

FIX: Add eigen and any as INTERFACE deps

* init etcd cclient

* add etcd

* add etcd.go

* fix compile problem

* move code to etcd.go

* add etcd_lister.go for pserver client

* add etcd_client_test.go

* merge etcd_client_test and client_test

* refine client_test.go

* refine code

* format code

* add TODO and use interface instead of struct

* fix typo of initDesiredPservers

* optimize dir structure of go/pserver/client

* add a flag to config index for pserver

* follow comment

* fix path

* optimize code

* remove err in pserver NewEtcd

* restore comment about /ps_desired

Add target_link_libraries for cc_library

It will fix #2728.

Maybe it is silly to `target_link_libraries` for static library,
because a static library do not need to link other libraries. But
it will tell cmake how to propagate dependencies.

The solution comes from
[here](http://floooh.github.io/2016/01/12/cmake-dependency-juggling.html).

* Also change op_proto_test DEPS for testing this fix works.

Add DEPS to `proto_library`

sort the Author.md with Alphabetical order

Missing DEPS will cause compile error when parallel is large.

* move net_design to framework

* change CreateNet result to unique_ptr

* rename "ScratchNet" -> "PlainNet"

* add three methods to NetBase

* add NetBuilder

* add InferShape to NetBuilder.Run

* rename ApplyGradient, ApplyOptimizer -> AddGradientOps, AddOptimiz

* rename PlainNet::CreateNet -> BuildNet

* add Error and other rename actions

Update new authors

Add OpProto implementation

Fix style check

Using glide for go package vendor

Go optimizer: integrate Go with optimizer library

OpProto is a proto message that helps 3rd-party language bindings, e.g.
`Python`, to generate operator creation methods. The operator creation
method is the low-level API for 3rd-party language bindings. Op creation
methods take the user's input in that language, and convert users inputs
into `OpDesc` message, then passing that `OpDesc` message to Paddle's
C++ core and create an operator.

* A separated `attr_type.proto` is added, because that file wound
  be included by `op_desc.proto` in future.

[draft] a simple op design doc