bump java environment to fix annotation compliance

the class StreamClientImpl (package: org.openhab.binding.sonos.internal) implements the following interface: StreamClient<StreamClientConfigurationImpl>

It adds implementation for the following functions:
public StreamClientConfigurationImpl getConfiguration();
public StreamResponseMessage sendRequest(StreamRequestMessage requestMessage);
public void stop();

The override annotation does not work for interfaces (see below).

IMHO: org.openhab.core already uses 1.6, so it should not break something to use that for a binding, too.

cite:
===
Well, there is a @Override annotation on one of the methods, but it
doesn’t have a superclass – it is annotating a method that is being
implemented (from an interface), not a method that is inherited (from a
superclass).

The @Override annotation is a Java 1.5 feature, and the error message I
was getting was coming (correctly) from a 1.5 compiler. However in Java
1.6 the @Override annotation can also be applied to methods that are
implemented from an interface.
===

Quote:
http://www.filsa.net/2008/02/11/maven-and-the-method-does-not-override-a-method-from-its-superclass-error/