cli: refactor cli related code

[shengofsun]

这个pr主要干的事情：

1. 以前cli是集成在core里面的。但这只是一个简单的rpc service，所以直接挪出来了。这样配置和core层的代码都好理解一些。
2. 以前command manager和rpc的处理是耦合的。现在解耦了，这样用别的方式来调用这些command也容易很多。（比如可以加个http的？)
3. cli的头文件和实现以前散落在不同地方，现在统一到了dist下。特别的，src/tools下面cli的一个小shell也放回到和cli模块一起。
4. 把cli_remote/cli_local这两个配置删了，相应的配置以后在新版本集群配置里也没必要了。

另外：

1. src/tools这个目录只剩下没用的repli了，这个pr就不动这个地方了。谁有空可以单独提个pr删一下。

[shengofsun]

这个attribute是s2编译需要的。不加的话gcc7编译不过

[neverchanje]

really nice job! but there're still something i doubt that need to fix:

first, since the _http_server is placed in meta_service_app, could the cli_service be placed there too? could you adapt the code style with the _http_server so we can make further refactoring easier?

second, why the cli_service have to call open_service after its constructor, like:

    // start cli service before acquiring leader lock,
    // so that the command line call can be handled
    _cli_service = std::move(dsn::cli_service::create_service());
    _cli_service->open_service();

why not just:

: _cli_service(new cli_service())

and in the constructor you can "open the service" and don't have to split up the logic into two different functions:

cli_service() : ::dsn::serverlet<cli_service>("cli") 
{
  register_async_rpc_handler(RPC_CLI_CLI_CALL, "call", &cli_service::on_call);
}

~cli_service() 
{
  unregister_rpc_handler(RPC_CLI_CLI_CALL);
}

[neverchanje]

call this dsn_cli_shell?

[shengofsun]

这个晚上我抽空改一下吧，白天没时间……

[shengofsun]

@neverchanje

1. "open_service" function for "xxx_service" is generated by the code generator, here we just keep the same with old conventions. We can modify this in a seperated pr after the code generator is refactored.
2. “putting the cli_service into meta_service and replica_stub” follows the old conventions, too. As all the services are handled by replica_stub & meta_service, only the "http_service" is an exception:-(

[neverchanje]

ok... and i will move http_service to meta_service after this committed.

[shengofsun]

@ALL has fixed based on comments