Remote service builder

[ruzkant]

This is a proposal to support the goals of issue #28, but an alternative approach to the RpcRequestBuilder from GWT 2. It follows the same pattern as the websocket ServerBuilder.

[ruzkant]

Neither the old factory nor ServiceDefTarget have been removed as yet.

One can keep ServiceDefTarget by adding the following to allow the url from service def target to be used, but support overriding it with the url from the builder. This makes it possible to add the old @RemoteServiceRelativePath annotation so the service would know the url from there (which is how I think GWT 2 works.

    String url = "";
    if (instance[0] instanceof ServiceDefTarget) {
        url = ((ServiceDefTarget) instance[0]).getServiceEntryPoint();
    }
    if(getUrl() != null) {
        url = getUrl();
    }