kubernetes provider (#772)

* feat: Kubernetes ServiceDiscoveryProvider

* 编写k8s测试例子

* feat：fix kube config

* feat： remove port

* feat ： complete the k8s test

* feat :  add kubeserviceDiscovery test

* feat : add kube provider unittest

* feat :add kubetnetes docs

how to use ocelot with kubetnetes docs

* keep the configuration as simple as possible, no qos, no cache

* fix: use http

* add PollingKubeServiceDiscovery

* feat : refactor logger

* feat : add  pollkube docs

* feat：Remove unnecessary code

* feat ： code-block json

test/Ocelot.AcceptanceTests/ServiceDiscoveryTests.cs

@@ -434,7 +434,8 @@
                         Host = "localhost",
                         Port = consulPort,
                         Type = "PollConsul",
-                        PollingInterval = 0
+                        PollingInterval = 0,
+                        Namespace = string.Empty
                     }
                 }
             };