Convert RegistrarServlet to RegistrarAction

Convert to an action and remove ResourceServlet, JsonTransportServlet and
JsonTransportServlet, all of which exist only to support it.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=137519385

java/google/registry/config/ConfigModule.java

@@ -17,6 +17,7 @@ package google.registry.config;
 import static google.registry.config.ConfigUtils.makeUrl;
 
 import com.google.common.base.Optional;
+import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableMap;
 import dagger.Module;
 import dagger.Provides;
@@ -325,6 +326,13 @@ public final class ConfigModule {
     }
   }
 
+  @Provides
+  @Config("registrarChangesNotificationEmailAddresses")
+  public static ImmutableList<String> provideRegistrarChangesNotificationEmailAddresses(
+      RegistryConfig config) {
+    return config.getRegistrarChangesNotificationEmailAddresses();
+  }
+
   /**
    * Returns the publicly accessible domain name for the running Google Apps instance.
    *

java/google/registry/config/RegistryConfig.java

@@ -163,7 +163,7 @@ public interface RegistryConfig {
    * Returns the email address(es) that notifications of registrar and/or registrar contact updates
    * should be sent to, or the empty list if updates should not be sent.
    *
-   * @see google.registry.ui.server.registrar.RegistrarServlet
+   * @see google.registry.ui.server.registrar.RegistrarAction
    */
   public ImmutableList<String> getRegistrarChangesNotificationEmailAddresses();