(GH-10) Backup configuration files

Backup configuration files as a native way to keep around the
configuration file so that it can be compared to the new one that
overwrite the old (based on the merge strategy from nuget). This is
naive yes, more of GH-10 will later handle this better.

src/chocolatey/infrastructure.app/ApplicationParameters.cs

@@ -61,6 +61,8 @@ public static class ApplicationParameters
         /// </summary>
         public static int DefaultWaitForExitInSeconds = 2700;
 
+        public static readonly string[] ConfigFileExtensions = new string[] {".autoconf",".config",".conf",".cfg",".jsc",".json",".jsonp",".ini",".xml",".yaml"};
+
         public static class Tools
         {
             //public static readonly string WebPiCmdExe = _fileSystem.combine_paths(InstallLocation, "nuget.exe");

src/chocolatey/infrastructure.app/services/NugetService.cs

@@ -612,6 +612,22 @@ public void backup_existing_version(ChocolateyConfiguration config, IPackage ins
                         this.Log().Error("Error during backup (reset phase):{0} {1}".format_with(Environment.NewLine, ex.Message));
                     }
                 }
+
+                backup_configuration_files(pkgInstallPath, installedPackage.Version.to_string());
+
+            }
+        }
+
+        private void backup_configuration_files(string packageInstallPath, string version)
+        {
+            var configFiles = _fileSystem.get_files(packageInstallPath, ApplicationParameters.ConfigFileExtensions, SearchOption.AllDirectories);
+            foreach (var file in configFiles.or_empty_list_if_null())
+            {
+                var backupName = "{0}.{1}.{2}".format_with(_fileSystem.get_file_name_without_extension(file), version, _fileSystem.get_file_extension(file));
+
+                FaultTolerance.try_catch_with_logging_exception(
+                    () => _fileSystem.copy_file(file, _fileSystem.combine_paths(_fileSystem.get_directory_name(file), backupName), overwriteExisting: true),
+                    "Error backing up configuration file");
             }
         }