SPI needs proxy services to support serialization/deserialization of proxies

A set of services are needed to allow containers to specify class loaders to use for proxy class generation and to load classes using the correct class loader during deserialization operations.

The interface for these services is org.jboss.weld.serialization.spi.ProxyServices.

A default implementation is provided that is currently suitable for JBoss AS and may work for some other containers as well. This implementation is org.jboss.weld.bean.proxy.util.SimpleProxyServices.