auto detect Scala version for non-cross-versioned launcher app

launch/interface/src/main/java/xsbti/AppProvider.java

@@ -9,6 +9,7 @@ public interface AppProvider
 	/** The ID of the application that will be created by 'newMain' or 'mainClass'.*/
 	public ApplicationID id();
 
+	 public ClassLoader loader();
 	/** Loads the class for the entry point for the application given by 'id'.  This method will return the same class
 	* every invocation.  That is, the ClassLoader is not recreated each call.*/
 	public Class<? extends AppMain> mainClass();

launch/interface/src/main/java/xsbti/Launcher.java

@@ -7,6 +7,7 @@ public interface Launcher
 	public static final int InterfaceVersion = 1;
 	public ScalaProvider getScala(String version);
 	public ScalaProvider getScala(String version, String reason);
+	public AppProvider app(ApplicationID id, String version);
 	public ClassLoader topLoader();
 	public GlobalLock globalLock();
 	public File bootDirectory();