Use KieRemoteHttp* instead of resteasy for kie-server-client

This PR does following things:
 * replaces the usage of resteasy-client with KieRemoteHttp[Request|Response] as this makes the client much more lightweight and usable inside other web applications (like kie-wb). I did basically something very similar to the stuff in kie-remote-client. In future we might want to unify some things into `kie-remote-common` so they could be reused. I did not want to bring the whole `kie-remote-client` and its dependencies.

 * in order to make serialization as easy as possible I had to change the `List<ServiceResponse>` for `ServiceResponsesList` in executeScript(). This make it much easier to define the Jaxb annotations so the jaxb/json can automatically marshall the list. This however breaks the API. Let me know if it is too late to change the API and we will need to work around that.

* additional refactoring were done to the `KieServicesClient` to better reuse the code and offer slightly better error handling

* I also added few unit tests just for the client to be able to quickly tell if something really bad happened during refactoring

* JSON dependencies were clean-up across the different modules. Now only needed dependencies are declared in the poms.

* @etirelli and @mrietveld please take a look and let me know what you think