Convert RequestRewriters to ResponseRewriters (issue1304042)

[johnfargo]

Reviewers: shindig.remailer_gmail.com,

Description:
Part #2 of move to ResponseRewriter interfaces.
Converts RequestRewriter implementations to ResponseRewriters instead.
Replaces RequestRewriterRegistry with ResponseRewriterRegistry, with
pre-cached ResponseRewriterRegistry independently registered.

Please review this at http://codereview.appspot.com/1304042/show

Affected files:
   
java/gadgets/src/main/java/org/apache/shindig/gadgets/http/AbstractHttpCache.java
   
java/gadgets/src/main/java/org/apache/shindig/gadgets/http/DefaultRequestPipeline.java
   
java/gadgets/src/main/java/org/apache/shindig/gadgets/render/SanitizingRequestRewriter.java
   
java/gadgets/src/main/java/org/apache/shindig/gadgets/render/old/SanitizingGadgetRewriter.java
   
java/gadgets/src/main/java/org/apache/shindig/gadgets/render/old/SanitizingRequestRewriter.java
   
java/gadgets/src/main/java/org/apache/shindig/gadgets/rewrite/CaptureRewriter.java
   
java/gadgets/src/main/java/org/apache/shindig/gadgets/rewrite/CssRequestRewriter.java
   
java/gadgets/src/main/java/org/apache/shindig/gadgets/rewrite/DefaultRequestRewriterRegistry.java
   
java/gadgets/src/main/java/org/apache/shindig/gadgets/rewrite/DomWalker.java
   
java/gadgets/src/main/java/org/apache/shindig/gadgets/rewrite/RequestRewriter.java
   
java/gadgets/src/main/java/org/apache/shindig/gadgets/rewrite/RequestRewriterRegistry.java
   
java/gadgets/src/main/java/org/apache/shindig/gadgets/rewrite/RewriteModule.java
   
java/gadgets/src/main/java/org/apache/shindig/gadgets/rewrite/RewriterUtils.java
   
java/gadgets/src/main/java/org/apache/shindig/gadgets/rewrite/old/CssRequestRewriter.java
   
java/gadgets/src/main/java/org/apache/shindig/gadgets/rewrite/old/HTMLContentRewriter.java
   
java/gadgets/src/main/java/org/apache/shindig/gadgets/servlet/ConcatProxyServlet.java
   
java/gadgets/src/main/java/org/apache/shindig/gadgets/servlet/HttpRequestHandler.java
   
java/gadgets/src/main/java/org/apache/shindig/gadgets/servlet/MakeRequestHandler.java
   
java/gadgets/src/main/java/org/apache/shindig/gadgets/servlet/ProxyHandler.java
   
java/gadgets/src/test/java/org/apache/shindig/gadgets/http/AbstractHttpCacheTest.java
   
java/gadgets/src/test/java/org/apache/shindig/gadgets/render/ProxyRendererTest.java
   
java/gadgets/src/test/java/org/apache/shindig/gadgets/render/SanitizingRequestRewriterTest.java
   
java/gadgets/src/test/java/org/apache/shindig/gadgets/render/old/SanitizingRequestRewriterTest.java
   
java/gadgets/src/test/java/org/apache/shindig/gadgets/rewrite/CssRequestRewriterTest.java
   
java/gadgets/src/test/java/org/apache/shindig/gadgets/rewrite/DefaultContentRewriterRegistryTest.java
   
java/gadgets/src/test/java/org/apache/shindig/gadgets/rewrite/RewriterTestBase.java
   
java/gadgets/src/test/java/org/apache/shindig/gadgets/rewrite/old/BaseRewriterTestCase.java
   
java/gadgets/src/test/java/org/apache/shindig/gadgets/rewrite/old/CssRequestRewriterTest.java
   
java/gadgets/src/test/java/org/apache/shindig/gadgets/rewrite/old/HTMLContentRewriterTest.java
   
java/gadgets/src/test/java/org/apache/shindig/gadgets/servlet/HttpRequestHandlerTest.java
   
java/gadgets/src/test/java/org/apache/shindig/gadgets/servlet/ProxyHandlerTest.java
   
java/gadgets/src/test/java/org/apache/shindig/gadgets/servlet/ServletTestFixture.java