Improve Installer to check for updates

com.unity.perception/Editor/GroundTruth/PerceptionCameraEditor.cs

-using System;
+using System;
 using System.Collections.Generic;
 using UnityEditorInternal;
 using UnityEngine;
                     GUIUtility.systemCopyBuffer = dir;
                 }
                 GUILayout.EndHorizontal();
+                if (GUILayout.Button("Open Visualizer"))
+                {
+                    UnityEditor.Perception.Visualizer.VisualizerInstaller.RunVisualizer();
+                }
                 GUILayout.EndVertical();
             }
 

com.unity.perception/Editor/Visualizer/PipAPI.cs

+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+using System.Net;
+using System.Net.Http;
+using System.Net.Http.Headers;
+using System.Text;
+using System.Threading;
+using System.Threading.Tasks;
+using Newtonsoft.Json;
+using Newtonsoft.Json.Linq;
+using Unity.Simulation.Client;
+using UnityEngine;
+
+namespace UnityEditor.Perception.Visualizer
+{
+    static class PipAPI
+    {
+        static readonly HttpClient k_HttpClient;
+        static string s_PypiServer = "https://pypi.org";
+        static string s_PackageName = "unity-cv-datasetvisualizer";
+
+        static PipAPI()
+        {
+            k_HttpClient = new HttpClient();
+        }
+
+        static internal async Task<string> GetLatestVersionNumber()
+        {
+			var requestUri = new Uri($"{s_PypiServer}/pypi/{s_PackageName}/json?Accept=application/json");
+			try
+            {
+            	var httpResponse = await k_HttpClient.GetAsync(requestUri);
+                if (httpResponse.IsSuccessStatusCode)
+                {
+                    var responseString = httpResponse.Content.ReadAsStringAsync().Result;
+                    dynamic responseJson = JsonConvert.DeserializeObject(responseString);
+                    return responseJson.info.version;
+                }
+                else
+                {
+                    HandleApiErrors(httpResponse);
+                }
+            }
+            catch (HttpRequestException e)
+            {
+                Debug.LogException(e);
+            }
+			return null;
+        }
+
+        static void HandleApiErrors(HttpResponseMessage responseMessage)
+        {
+            Debug.LogError("A request to PyPI.org did not successfully complete: " + responseMessage.ReasonPhrase);
+        }
+
+        static internal int compareVersions(string version1, string version2)
+        {
+            string[] split1 = version1.Split('.');
+            string[] split2 = version2.Split('.');
+
+            if(split1.Length != split2.Length)
+            {
+                throw new ArgumentException($"Can't compare two versions that do not have the same format: {version1} & {version2}");
+            }
+
+            for(int i = 0; i < split1.Length; i++)
+            {
+                int compare = Int32.Parse(split1[i]) - Int32.Parse(split2[i]);
+                if (compare != 0)
+                {
+                    return compare;
+                }
+            }
+            return 0;            
+        }
+    }
+}