Updates to use Java 7
Updates to use Java 7

Reviewed in https://codereview.appspot.com/11456043/

robotfoot/wdf-appengine,GoogleCloudPlatform/appengine-endpoints-helloendpoints-java-maven,WalkerIX/restMe,fbelzunc/appengine-endpoints-helloendpoints-java-maven,fbelzunc/appengine-endpoints-helloendpoints-java-maven,robotfoot/wdf-appengine,GoogleCloudPlatform/appengine-endpoints-helloendpoints-java-maven,GoogleCloudPlatform/appengine-endpoints-helloendpoints-java-maven,robotfoot/wdf-appengine,fbelzunc/appengine-endpoints-helloendpoints-java-maven,WalkerIX/restMe,WalkerIX/restMe