Fix assembly versioning/properties and handle platform exception (#1660)

* Use assembly version instead of hard-coded ones

Builds happening on AppVeyor specify the assembly version with `dotnet build /p:Version=<gitversion>`

* Set default version for dev time

This is to avoid that the default 1.0.0 version be assigned to the assemblies

* Move various package/assembly properties from AssemblyInfo into csproj files so dotnet build can set them all

* Get rid of SolutionInfo and move assembly version function into Connection class

* Rework FormatUserAgent to use InformationalVersion and guard against exceptions determining platform OS/arch (fixes #1617)

* Update assembly descriptions

* Reword dotnetcore to .NET Core

* Attempted workaround for package version dependency issue by specifying version on dotnet restore
see https://github.com/NuGet/Home/issues/4337

Octokit/Http/Connection.cs

@@ -4,6 +4,7 @@ using System.Globalization;
 using System.Linq;
 using System.Net;
 using System.Net.Http;
+using System.Reflection;
 using System.Threading;
 using System.Threading.Tasks;
 using Octokit.Internal;
@@ -696,26 +697,60 @@ namespace Octokit
 
         static string FormatUserAgent(ProductHeaderValue productInformation)
         {
-            var format =
-#if !HAS_ENVIRONMENT
-                "{0} ({1}; {2}; {3}; Octokit {4})";
-#else
-                "{0} ({1} {2}; {3}; {4}; Octokit {5})";
-#endif
-
-            return string.Format(CultureInfo.InvariantCulture,
-                format,
+            return string.Format(CultureInfo.InvariantCulture, "{0} ({1}; {2}; Octokit {3})",
                 productInformation,
+                GetPlatformInformation(),
+                GetCultureInformation(),
+                GetVersionInformation());
+        }
+
+        private static string _platformInformation;
+        static string GetPlatformInformation()
+        {
+            if (string.IsNullOrEmpty(_platformInformation))
+            {
+                try
+                {
+                    _platformInformation = string.Format(CultureInfo.InvariantCulture,
 #if !HAS_ENVIRONMENT
-                RuntimeInformation.OSDescription,
-                RuntimeInformation.OSArchitecture.ToString().ToLowerInvariant(),
+                        "{0}; {1}",
+                        RuntimeInformation.OSDescription.Trim(),
+                        RuntimeInformation.OSArchitecture.ToString().ToLowerInvariant().Trim()
 #else
-                Environment.OSVersion.Platform,
-                Environment.OSVersion.Version.ToString(3),
-                Environment.Is64BitOperatingSystem ? "amd64" : "x86",
+                        "{0} {1}; {2}",
+                        Environment.OSVersion.Platform,
+                        Environment.OSVersion.Version.ToString(3),
+                        Environment.Is64BitOperatingSystem ? "amd64" : "x86"
 #endif
-                CultureInfo.CurrentCulture.Name,
-                AssemblyVersionInformation.Version);
+                        );
+                }
+                catch
+                {
+                    _platformInformation = "Unknown Platform";
+                }
+            }
+
+            return _platformInformation;
+        }
+
+        static string GetCultureInformation()
+        {
+            return CultureInfo.CurrentCulture.Name;
+        }
+
+        private static string _versionInformation;
+        static string GetVersionInformation()
+        {
+            if (string.IsNullOrEmpty(_versionInformation))
+            {
+                _versionInformation = typeof(IGitHubClient)
+                    .GetTypeInfo()
+                    .Assembly
+                    .GetCustomAttribute<AssemblyInformationalVersionAttribute>()
+                    .InformationalVersion;
+            }
+
+            return _versionInformation;
         }
     }
 }