Limited invalidation support

[lo...@gmail.com]

Reviewers: shindig-dev, awiner, beaton, panjie,

Description:
This is an initial implementation of the "Limited Invalidation" spec.
Containers are expected to implement their own InvalidationService based
on their caching behavior

This implementation differs from the spec in a couple of ways that I
believe are worth proposing as clarifications.
- The service endpoint is "cache/invalidate" not "invalidate" for REST.
For RPC the method is "cache.invalidate"
- Only 2-legged consumer OAuth calls can invalidate URLs
- Security token for rendering gadgets can only be used to invalidate
the viewers data
-  Viewer data is invalidated by default and a simple GET
/social/rest/cache/invalidate will trigger it

The default request pipeline is altered to allow invalidated content to
be returned if fetching a replacement causes an error as is suggested in
the spec.

Please review this at http://codereview.appspot.com/23041

Affected files:
    
java/common/src/main/java/org/apache/shindig/auth/AnonymousAuthenticationHandler.java
    
java/common/src/main/java/org/apache/shindig/auth/AnonymousSecurityToken.java
    
java/common/src/main/java/org/apache/shindig/auth/AuthenticationHandler.java
   java/common/src/main/java/org/apache/shindig/auth/AuthenticationMode.java
   java/common/src/main/java/org/apache/shindig/auth/BasicSecurityToken.java
    
java/common/src/main/java/org/apache/shindig/auth/BlobCrypterSecurityToken.java
   java/common/src/main/java/org/apache/shindig/auth/SecurityToken.java
    
java/common/src/main/java/org/apache/shindig/auth/UrlParameterAuthenticationHandler.java
    
java/common/src/main/java/org/apache/shindig/protocol/DefaultHandlerRegistry.java
    
java/common/src/test/java/org/apache/shindig/common/testing/FakeGadgetToken.java
    
java/gadgets/src/main/java/org/apache/shindig/gadgets/http/DefaultInvalidationService.java
    
java/gadgets/src/main/java/org/apache/shindig/gadgets/http/DefaultRequestPipeline.java
    
java/gadgets/src/main/java/org/apache/shindig/gadgets/http/InvalidationHandler.java
    
java/gadgets/src/main/java/org/apache/shindig/gadgets/http/InvalidationService.java
    
java/gadgets/src/main/java/org/apache/shindig/gadgets/http/NoOpInvalidationService.java
    
java/gadgets/src/main/java/org/apache/shindig/gadgets/servlet/ProxyHandler.java
    
java/gadgets/src/test/java/org/apache/shindig/gadgets/http/DefaultInvalidationServiceTest.java
    
java/gadgets/src/test/java/org/apache/shindig/gadgets/http/DefaultRequestPipelineTest.java
    
java/gadgets/src/test/java/org/apache/shindig/gadgets/http/InvalidationHandlerTest.java
    
java/server/src/test/java/org/apache/shindig/server/endtoend/EndToEndModule.java
    
java/social-api/src/main/java/org/apache/shindig/social/core/config/SocialApiGuiceModule.java
    
java/social-api/src/main/java/org/apache/shindig/social/core/oauth/OAuthAuthenticationHandler.java
    
java/social-api/src/main/java/org/apache/shindig/social/core/oauth/OAuthConsumerRequestAuthenticationHandler.java
    
java/social-api/src/main/java/org/apache/shindig/social/core/oauth/OAuthSecurityToken.java
    
java/social-api/src/main/java/org/apache/shindig/social/sample/oauth/SampleOAuthDataStore.java
    
java/social-api/src/test/java/org/apache/shindig/social/SocialApiTestsGuiceModule.java