Tooling API: Allow to explicitly retrieve information about unresolved dependencies

The Tooling API doesn't allow to get information about unresolved third-party dependencies. Here is a simple test that illustrates that:

1. Go to $GRADLE_HOME/samples/java/quickstart;
2. Define, say, version '10.2' for 'commons-collections' dependency at 'build.gradle' there;
3. Start the program below:

   package org.jetbrains.plugins.gradle;
   
   import org.gradle.tooling.GradleConnector;
   import org.gradle.tooling.ModelBuilder;
   import org.gradle.tooling.ProjectConnection;
   import org.gradle.tooling.model.idea.*;
   
   import java.io.File;
   
   /**
    * @author Denis Zhdanov
    * @since 12/8/11 5:07 PM
    */
   public class GradleStartClass {
   
     private static final String GRADLE_PROJECT_PATH = "/home/denis/dev/gradle/gradle-1.0-milestone-6/samples/java/quickstart";
   
     public static void main(String[] args) {
       test("/home/denis/dev/gradle/gradle-1.0-milestone-6"); // Don't expect exception here
     }
   
     private static void test(String gradleHome) {
       GradleConnector connector = GradleConnector.newConnector();
       connector.useInstallation(new File(gradleHome));
       connector.forProjectDirectory(new File(GRADLE_PROJECT_PATH));
       ProjectConnection connection = connector.connect();
       ModelBuilder<? extends IdeaProject> modelBuilder = connection.model(IdeaProject.class);
       IdeaProject project = modelBuilder.get();
       for (IdeaModule module : project.getModules()) {
         for (IdeaDependency dependency : module.getDependencies()) {
           if (dependency instanceof IdeaModuleDependency) {
             continue;
           }
           System.out.printf("Dependency: %s%n", ((IdeaSingleEntryLibraryDependency)dependency).getFile());
         }
       }
     }
   }

Output:

Dependency: unresolved dependency - commons-collections#commons-collections;10.2
Dependency: /home/denis/.gradle/caches/artifacts-4/junit/junit/c12498cf18507aa6433a94eb7d3e77d5/jars/junit-4.10.jar
Dependency: /home/denis/.gradle/caches/artifacts-4/org.hamcrest/hamcrest-core/c12498cf18507aa6433a94eb7d3e77d5/jars/hamcrest-core-1.1.jar