Fixes for findbugs issues in shindig/java/gadgets (issue1712045)

[janluehe]

Reviewers: dev-remailer_shindig.apache.org,

Description:
Incremental fix for https://issues.apache.org/jira/browse/SHINDIG-1374,
which addresses the following bugs:
Method
org.apache.shindig.gadgets.uri.DefaultConcatUriManager.makeConcatUri(ConcatUriManager$ConcatUri,
boolean, String) invokes inefficient new Integer(int) constructor; use
Integer.valueOf(int) instead

Method
org.apache.shindig.gadgets.uri.DefaultConcatUriManager.process(Uri)
invokes inefficient new Integer(int) constructor; use
Integer.valueOf(int) instead

org.apache.shindig.gadgets.servlet.HttpGadgetContext.getDebug(HttpServletRequest)
has Boolean return type and returns explicit null

org.apache.shindig.gadgets.servlet.HttpGadgetContext.getIgnoreCache(HttpServletRequest)
has Boolean return type and returns explicit null

org.apache.shindig.gadgets.servlet.ConcatProxyServlet.doFetchConcatResources(HttpServletResponse,
ConcatUriManager$ConcatUri) may fail to close stream

Suspicious comparison of Boolean references in
org.apache.shindig.gadgets.features.FeatureRegistry$FeatureCacheKey.equals(Object)

Call to equals() comparing different types in
org.apache.shindig.gadgets.http.HttpResponseBuilder.setEncoding(Charset)        

Should
org.apache.shindig.gadgets.servlet.ConcatProxyServlet$RequestContext be
a _static_ inner class? 

org.apache.shindig.gadgets.uri.ProxyUriBase defines equals and uses
Object.hashCode()       

org.apache.shindig.gadgets.uri.ProxyUriManager$ProxyUri defines equals
and uses Object.hashCode()

Please review this at http://codereview.appspot.com/1712045/show

Affected files:
   
java/gadgets/src/main/java/org/apache/shindig/gadgets/features/FeatureRegistry.java
   
java/gadgets/src/main/java/org/apache/shindig/gadgets/http/HttpResponseBuilder.java
   
java/gadgets/src/main/java/org/apache/shindig/gadgets/servlet/ConcatProxyServlet.java
   
java/gadgets/src/main/java/org/apache/shindig/gadgets/servlet/HttpGadgetContext.java
   
java/gadgets/src/main/java/org/apache/shindig/gadgets/uri/ConcatUriManager.java
   
java/gadgets/src/main/java/org/apache/shindig/gadgets/uri/DefaultConcatUriManager.java
   
java/gadgets/src/main/java/org/apache/shindig/gadgets/uri/ProxyUriBase.java