Reimplement the RDAP Json creation using Jsonables

Currently we try to reimplemnet the same behavior of the existing code as much
as possible.

We only fix issues that go against the RFC7483, but we don't yet update the
code to follow the latest (15feb19) RDAP Response Profile. That will require a
much bigger change especially for the test files, so it'll wait for a followup
CL.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=246948018

java/google/registry/request/RequestModule.java

@@ -96,6 +96,12 @@ public final class RequestModule {
     return req.getRequestURI();
   }
 
+  /**
+   * Returns the part of this request's URL that calls the servlet.
+   *
+   * <p>This includes the path to the servlet, but does not include any extra path information or a
+   * query string.
+   */
   @Provides
   @FullServletPath
   static String provideFullServletPath(HttpServletRequest req) {