add ability for ribbon/eureka to use ipAddr instead of hostName configed...

add ability for ribbon/eureka to use ipAddr instead of hostName configed via Archaius

this relates to the discussion on the mailing list here:

https://groups.google.com/forum/#!topic/eureka_netflix/7M28bK-SCZU
This will expect a global property for all Ribbon clients in the same JVM to use IP address. However, we would like to be able to set this property for individual clients.

The way it works should follow the pattern of properties defined in DefaultClientConfigImpl:

1. Defined the property as a key in CommonClientConfigKey
2. Load its default value (which should be "false") in DefaultClientConfigImpl
3. use clientConfig.getProperty() to access it