The zone for a remote server comes from its
eureka.instance.metadataMap.zone, but we didn't (until this change)
apply the same logic to the client. If the client is registering
itslef with eureka then it will have a metadataMap itself and
we should be able to just reverse the logic.

Fixes gh-991

Route specific sensitiveHeaders override global.

fixes gh-944

When fallback beans are created, there was no longer a unique bean of the feign interface which caused autowire problems.

fixes gh-899

`DiscoveryClient` field declared with name `discoveryClient` but `serviceUrl()` method uses `client`.

Support for Single via a ReturnValueHandler.
Support for Observable via SseEmitter.

By default we now discard all Set-Cookie and Cookie headers. User
can manipulate it per route via zuul.routes.*.sensitiveHeaders, or
globally via zuul.ignoredHeaders.

Latest Eureka from Netflix uses a different HTTP client, and it
ignores the HTTP basic credentials in a service URL. This change
partially restores the old behaviour by providing an interceptor
(ClientFilter) that has a single, global username/password
taken from the first serviceUrl that contains credentials.

Fixes gh-849

Add the ability to configure the max connections and max per route on PoolingHttpClientConnectionManager.

Eureka supports native placeholders, but Spring can also be used.
Added some docs to show how more explicitly.

See gh-761

Added @FeignClient(fallback).

Renamed FeignClientFactory to FeignContext.

fixes gh-762

fixes gh-693

fixes gh-717

Includes name and url attributes.

fixes gh-414

Reword to avoid broken AsciiDoc formatting.

User can provide a url in the route that starts with "forward:"
(instead of "http:" etc.) to handle the request locally.

Also properly ignores ignored routes, so they can be handled locally
(rather than giving up and sending 404).

Fixes gh-536

Since all feign clients now have access to the type, logging can apply a type regardless.

Fixes gh-431

Similar to @RibbonClient

fixes gh-288

There are usually some hints available, especially if the Server
came from Eureka. Unfortunately Server on it's own doesn't contain
enough information (why?), but as a fallback we can guess that
anyone using port 443 is secure.

Fixes gh-459

If the configserver registers with securePortEnabled=true we should
respect that in the discovery process.

Fixes gh-450

Change EurekaInstanceConfig.getSID to getInstanceId

fixes gh-554