Adds property zuul.sslHostnameValidationEnabled to be able to disable the hostname validation in the simpleHostRoutingFilter

fixes gh-1057

Previously ProxyRequestHelper contained a TraceRepository field. This caused zuul apps to fail with a class not found exception if they excluded actuator. This splits TraceRepository functionality into a new TraceProxyRequestHelper that extends ProxyRequestHelper. Auto configuration creates the appropriate ProxyRequestHelper based on the existence or not of actuator classes.

fixes gh-1135

Also added descriptions to properties.

fixes gh-1131

* schemeless-uri:
  Without explicit client config of IsSecure, lookup from registration

instead of defaulting to false.

Fixes gh-1126

Zuul sets an empty entity for GET requests. The apache http client either sets transfer encoding to chunked or a content length header. This change sets the apache entity contentLength to 0 (not the header), to that in RequestContent the "content-length" header is set to 0 rathern than transfer encoding.

See gh-1042

fixes gh-1113

See https://github.com/Netflix/Hystrix/issues/1251

If the content length isn't set on the entity, when http client determines which header to set, it sets transfer-encoding to chunked rather than content-length.

This fixes a missing content-length issue when using `HttpClientRibbonCommandFactory`.

See gh-1042

Updates so CloudJacksonJson extension is properly recognized by Eureka
Server as LegacyJacksonJson.

see gh-978
fixes gh-1111

It isn't very helpful to have a Collection converted to a String
anyway. We need to implement something new in Feign to apply
the converter (expander) to individual elements in the collection
but this change should get back to the old behaviour with
List<String> at least.

Fixes gh-1115

fixes gh-1110

* fix-query-string-in-class-requestmapping:
  Support path parms in Class @RequestMapping for feign

This commit adds the support to SpringMvcContract for path parameters
defined in the class' @RequestMapping Annotation that is applied to all
methods of a feign interface.

fixes gh-1023

Fixes gh-936

Fixes gh-1084

* Added missing error code for SimpleHostRoutingFilter
* Added missing error code for RibbonRoutingFilter

fixes gh-1051

So that it can handle multi-part requests that do not have a
file name.

Fixes gh-1067

Fixes gh-1076

Fixes gh-1080