added preferIpAddress section to eureka and updated ribbon docs to show what beans are created by default and how to override them.

 This includes support for: ServerList, ServerListFilter, IRule, IPing and IClientConfig.
 Eliminates custom wrapping of ServerList.

 fixes gh-185

fixes gh-144

update sidecare enabled property, make eureka portion of config conditional on eureka on classpath so other DiscoveryClient impls can use it.

fixes gh-159

fixes gh-179

fixes gh-180

fixes gh-182

Add feign-slf4j support.

fixes gh-178

The main problem here was the ZuulProperties being used everywhere. I also
took the opportunity to thin out the top level zuul package and keep the
web and route locator pieces in sub-packages for readability.

Fixes gh-172

A cleaner separation of ribbon and the eureka-dependent ribbon
configuration is achieved by adding a BeanPostProcessor to do the
ServerList wrapping, instead of doing it for every single ribbon
client.

See gh-172

proxy DiscoveryHeartbeatEvent's from parent to child be publishing a EurekaHeartbeatEvent and having zuul listen for EurekaHeartbeatEvent as well.

fixes gh-171

Fixes gh-153

fixes gh-153

Fixes gh-160

 fixes gh-147

fixes gh-149

Conflicts:
	spring-cloud-netflix-core/src/main/java/org/springframework/cloud/netflix/feign/FeignClient.java
	spring-cloud-netflix-core/src/main/java/org/springframework/cloud/netflix/feign/FeignClientScan.java
	spring-cloud-netflix-core/src/main/java/org/springframework/cloud/netflix/zuul/filters/route/RibbonRoutingFilter.java
	spring-cloud-netflix-turbine-amqp/src/test/java/org/springframework/cloud/netflix/turbine/amqp/AggregatorTest.java

This change adds an ApplicationListener that sets some high priority
properties in the Environment to allow server.port and management.port
to keep their usual meaning, but have server.port apply only to turbine.
Actuator endpoints can be enabled with management.port (different to
server.port otherwise there will be a conflict between Netty and Tomcat).

Fixes gh-143, fixes gh-140

Fixes gh-151

Fixes gh-156

fixes gh-129