Enables use of Spring's `HttpInvoker` extension points to present the `principal` and `credentials` located in the `ContextHolder` via BASIC authentication.

The beans are wired as follows:

`<bean id="test" class="org.springframework.remoting.httpinvoker.HttpInvokerProxyFactoryBean">
<property name="serviceUrl"><value>http://localhost/Test</value></property>
<property name="serviceInterface"><value>test.TargetInterface</value></property>
<property name="httpInvokerRequestExecutor"><ref bean="httpInvokerRequestExecutor"/></property>
</bean>
<bean id="httpInvokerRequestExecutor" class="net.sf.acegisecurity.ui.httpinvoker.AuthenticationSimpleHttpInvokerRequestExecutor"/>
`