Some of org.jboss.weld.environment.se.Weld fields should be probably protected

Users are allowed to extend org.jboss.weld.environment.se.Weld and override Weld.createDeployment() method. However, a subclass cannot access the private fields such as properties or extensions. We should either disallow to extend org.jboss.weld.environment.se.Weld (that's not backward compatible) or change some modifiers so that the overriding makes sense. Also the example in Weld.createDeployment() javadoc is not ideal - ResourceLoader could be set through Weld.setResourceLoader(ResourceLoader) method.