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

samples/OelotKube/ApiGateway/Startup.cs

@@ -0,0 +1,36 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading.Tasks;
+using Microsoft.AspNetCore.Builder;
+using Microsoft.AspNetCore.Hosting;
+using Microsoft.AspNetCore.Http;
+using Microsoft.Extensions.DependencyInjection;
+using Ocelot.DependencyInjection;
+using Ocelot.Middleware;
+using Ocelot.Provider.Kubernetes;
+
+namespace ApiGateway
+{
+    public class Startup
+    {
+        // This method gets called by the runtime. Use this method to add services to the container.
+        // For more information on how to configure your application, visit https://go.microsoft.com/fwlink/?LinkID=398940
+        public void ConfigureServices(IServiceCollection services)
+        {
+            services.AddOcelot()
+                .AddKubernetes();
+        }
+
+        // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
+        public void Configure(IApplicationBuilder app, IHostingEnvironment env)
+        {
+            if (env.IsDevelopment())
+            {
+                app.UseDeveloperExceptionPage();
+            }
+
+            app.UseOcelot().Wait();
+        }
+    }
+}