It seems like a generic feature to me (not specific to the proxy),
so logically it should live in the base class.

Fixes gh-844

The super class deals with syncing to peers, so we need that
call. It still delegates to the other register method and seems
to work just fine without the override.

Fixes gh-838

* simplefilter-connection-settings-config:
  Add the ability to configure the max connections and max per route on PoolingHttpClientConnectionManager.

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

See corresponding change in s-c-commons https://github.com/spring-cloud/spring-cloud-commons/commit/539a537abba58ed2261c4485d7f9426d2aa57453

fixes gh-643

See gh-826

User can exclude headers (generally in responses is most useful)
by configuring them, or calling a setter in ZuulProperties.

If Spring Security is on the classpath we add a few headers
automatically, corresponding to the ones that would be added
by Spring Security in the remote backend anyway (so they are not
added twice). Nothing is actually removed, so if the remote
service doesn't add those headers, we don't change anything.

The X-Application-Context header is also added to the hard coded
list of ignored headers, because it isn't relevant in the
gateway (and leaks information about the remote service).

Fixes gh-819

Plus polish

fixes gh-836

Fixes gh-803 (again)

Otherwise there can be duplicate beans with the same type and different
names, becasue the autoconfig does not (for some reason) use
@EnableConfigurationProperties to create the ServerProperties bean.

It isn't an issue until someone writes some autoconfig that itself
imports the ZuulConfiguration (i.e. regular concious users of
@EnableZuulServer do not see any problems and hence no tests fail
here or in integration projects).

Fixes gh-821

I.e. show empty "foo" as foo (not foo=)

Fixes gh-825

fixes gh-822

fixes gh-406

fixes gh-813

fixes gh-809

Upgrading feign

Also does not rename another one because it fails (see gh-804). The
bug can be fixed in feign (https://github.com/Netflix/feign/pull/324),
and if that gets merged and released we can revert some of the recent
changes to the apache load balancer here.

fixes gh-807

See https://github.com/spring-cloud/spring-cloud-build/issues/26

Fix typo: zule-core -> zuul-core.