Moved guice extension from incubator to modules.
Added package-info.java.
Updated module.xml.
Removed example subpackage.
Guice extension builds in jse and jee

module.xml label -> name
Added javax.inject jar.
README truncated and now refers to package-info.java
Package-info updated.
Merge pull request #877 from restlet/promote-guice-extension

Promote Guice extension