Add AndroidSdkInfo.DetectAndSetPreferredJavaSdkPathToLatest()

Context: https://paper.dropbox.com/doc/OpenJDK-and-You--AH1yWKdVXgno~uXYfmcUAZTwAg-NoECAe2XkBQeoxFfGL6ea

Add `AndroidSdkInfo.DetectAndSetPreferredJavaSdkPathToLatest()`.

Author: jonpryor

src/Xamarin.Android.Tools.AndroidSdk/AndroidSdkInfo.cs

@@ -171,5 +171,20 @@ public static void SetPreferredJavaSdkPath (string path, Action<TraceLevel, stri
 			var sdk = CreateSdk (logger);
 			sdk.SetPreferredJavaSdkPath (path);
 		}
+
+		public static void DetectAndSetPreferredJavaSdkPathToLatest (Action<TraceLevel, string> logger = null)
+		{
+			if (OS.IsWindows)
+				throw new NotSupportedException ("Windows is not supported at this time.");
+
+			logger          = logger ?? DefaultConsoleLogger;
+
+			var latestJdk   = JdkInfo.GetMacOSMicrosoftJdks (logger).FirstOrDefault ();
+			if (latestJdk == null)
+				throw new NotSupportedException ("No preferred Java SDK could be found.");
+
+			var sdk = CreateSdk (logger);
+			sdk.SetPreferredJavaSdkPath (latestJdk.HomePath);
+		}
 	}
 }

src/Xamarin.Android.Tools.AndroidSdk/JdkInfo.cs

@@ -236,7 +236,7 @@ static IEnumerable<string> GetConfiguredJdkPaths (Action<TraceLevel, string> log
 			}
 		}
 
-		static IEnumerable<JdkInfo> GetMacOSMicrosoftJdks (Action<TraceLevel, string> logger)
+		internal static IEnumerable<JdkInfo> GetMacOSMicrosoftJdks (Action<TraceLevel, string> logger)
 		{
 			return GetMacOSMicrosoftJdkPaths ()
 				.Select (p => TryGetJdkInfo (p, logger))