support dubbo-curl to send dubbo requests quickly

[randy]

We need a curl-like tool to send dubbo requests quickly which can be used in dubbo api test.

the cmd may be like.

dubbo-curl -X POST 'http://localhost:8883/UserService/com.dubbogo.pixiu.UserService/GetUserByName'  \
-d '{"types":"string","values":"tc"}' \
-H 'Content-Type: application/json'  \
-H 'x-dubbo-http1.1-dubbo-version':'1.0.0' \ 
-H 'x-dubbo-service-protocol':"dubbo"  \
-H 'x-dubbo-service-version':'1.0.0'  \
-H 'x-dubbo-service-group':'test'