Clean up Preload Java APIs

[awiner]

Reviewers: shindig-dev,


Please review this at http://codereview.appspot.com/17075

Affected files:
  M     features/core.io/io.js
  M     features/core.io/iotest.js
  M      
java/gadgets/src/main/java/org/apache/shindig/gadgets/FetchResponseUtils.java
  M     java/gadgets/src/main/java/org/apache/shindig/gadgets/Gadget.java
  M      
java/gadgets/src/main/java/org/apache/shindig/gadgets/preload/ConcurrentPreloaderService.java
  M      
java/gadgets/src/main/java/org/apache/shindig/gadgets/preload/ConcurrentPreloads.java
  M      
java/gadgets/src/main/java/org/apache/shindig/gadgets/preload/HttpPreloader.java
  D      
java/gadgets/src/main/java/org/apache/shindig/gadgets/preload/NullPreloads.java
  M      
java/gadgets/src/main/java/org/apache/shindig/gadgets/preload/PipelinedDataPreloader.java
  M      
java/gadgets/src/main/java/org/apache/shindig/gadgets/preload/PreloadedData.java
  M      
java/gadgets/src/main/java/org/apache/shindig/gadgets/preload/PreloaderService.java
  D      
java/gadgets/src/main/java/org/apache/shindig/gadgets/preload/Preloads.java
  M      
java/gadgets/src/main/java/org/apache/shindig/gadgets/render/HtmlRenderer.java
  M      
java/gadgets/src/main/java/org/apache/shindig/gadgets/render/RenderingContentRewriter.java
  M      
java/gadgets/src/main/java/org/apache/shindig/gadgets/rewrite/PipelineDataContentRewriter.java
  M      
java/gadgets/src/main/java/org/apache/shindig/gadgets/servlet/MakeRequestHandler.java
  M      
java/gadgets/src/test/java/org/apache/shindig/gadgets/FetchResponseUtilsTest.java
  M      
java/gadgets/src/test/java/org/apache/shindig/gadgets/preload/ConcurrentPreloaderServiceTest.java
  M      
java/gadgets/src/test/java/org/apache/shindig/gadgets/preload/ConcurrentPreloadsTest.java
  M      
java/gadgets/src/test/java/org/apache/shindig/gadgets/preload/HttpPreloaderTest.java
  M      
java/gadgets/src/test/java/org/apache/shindig/gadgets/preload/PipelinedDataPreloaderTest.java
  M      
java/gadgets/src/test/java/org/apache/shindig/gadgets/render/HtmlRendererTest.java
  M      
java/gadgets/src/test/java/org/apache/shindig/gadgets/render/RenderingContentRewriterTest.java
  M      
java/gadgets/src/test/java/org/apache/shindig/gadgets/rewrite/PipelineDataContentRewriterTest.java