SherlockTheme needed! MainActivity: now ABS ready!

- android:theme="@style/Sherlock.__Theme.DarkActionBar" > needed when
using ActionBarSherlock (tip in compile error)
- MainActivity now uses classes of com.actionbarsherlock like:
+import com.actionbarsherlock.app.ActionBar;
+import com.actionbarsherlock.app.ActionBar.Tab;
+import com.actionbarsherlock.app.SherlockListActivity;
+import com.actionbarsherlock.view.Menu;
+import com.actionbarsherlock.view.MenuInflater;
+import com.actionbarsherlock.view.MenuItem;

Also using now from supportlib:
+import android.support.v4.app.FragmentTransaction;

- no use of  getActionBarHelper anymore. Check with DonActionBarDemo!
-