Add WHOIS disclaimer text to ConfigModule

This fixes #23 for @parsoj by allowing a custom disclaimer to be
specified via dependency injection modules.

By making the disclaimer part of the dependency injection graph, it can
come from anywhere.

For example, if I was Donuts, I would have my own repository. I'd use an
external http_archive() repository for Domain Registry. Then I would
write my own Dagger @Component for each App Engine module. My Component
would have a list of Dagger Modules, which I copied from the Domain
Registry version. Then I would swap out ConfigModule with my own
DonutsConfigModule, which provides the same values.

So long as a method exists that @Provides @Config("whoisRegistry"), and
the module containing it is listed in the @Component, the dependency
injection graph becomes valid and complete for the whois package
(provided other dependencies are met.)

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=128082921

javatests/google/registry/whois/WhoisHttpServerTest.java

@@ -70,6 +70,7 @@ public class WhoisHttpServerTest {
     result.expires = Duration.standardHours(1);
     result.requestPath = WhoisHttpServer.PATH + pathInfo;
     result.response = response;
+    result.disclaimer = "Doodle Disclaimer";
     return result;
   }