Upgrading to Java 7.
Upgrading servlet to version 3.1.
Removed websocket support for Grizzly 1.9.
Using a servlet context listener to initialize the Dagger servlet.

- The initialization code which was performed by the servlet itself was moved to the new DaggerServletContextListener class.

- Plugin support, which was also handled by the servlet, was removed.  It will be replaced by a similar mechanism called "features" which will be handled by the servlet context listener.
Minor refactoring.
Reduce log verbosity during execution of unit tests.
Introducing servlet features mechanism.

Servlet features are much like plugins. The list of servlet feature classes is declared as a servlet context parameter, they are enabled during initialization of the servlet context.
Minor refactoring.
Minor code reorganization.
Added sample servlet feature manager configuration to the sample project.
Minor code reorganization.
Revert previous minor code reorganization. The XML schema validator was complaining about the position of the <listener> element.
Move the ServletFeature interface to the package 'dagger.servlet3.features'.
Make sure that the servlet feature manager receives the correct servlet context when enabling features.
Servlet features need a servlet context on enable().
Move test feature classes up to the 'features' subpackage.
Merge branch 'feature/servlet-3.1' into develop