add swagger support to dubbo ops

[Minxuan Zhuang]

I've add simple swagger support to restful controller through this
<https://github.com/apache/incubator-dubbo-ops/commit/755f6d9138f7efc059fd389f64f65d6b2c67648d>
commit, once the project is deployed, you can find restful api information
on page "http://localhost:8080/swagger-ui.html/";