add bunch of new java APIs: mostly stubs or copied from AOSP

Many of these classes are only needed to be subclassed by androidx
support library, which is used in many android apps

src/api-impl/android/app/Activity.java

@@ -1,5 +1,6 @@
 package android.app;
 
+import android.R;
 import android.content.ComponentName;
 import android.content.Context;
 import android.content.Intent;
@@ -102,6 +103,7 @@ public class Activity extends Context {
 
 	protected void onCreate(Bundle savedInstanceState) {
 		System.out.println("- onCreate - yay!");
+		new ViewGroup(this).setId(R.id.content);
 
 		return;
 	}
@@ -263,6 +265,22 @@ public class Activity extends Context {
 		nativeFinish(getWindow().native_window);
 	}
 
+	public Object getLastNonConfigurationInstance() {
+		return null;
+	}
+
+	public FragmentManager getFragmentManager() {
+		return new FragmentManager();
+	}
+
+	public LayoutInflater getLayoutInflater() {
+		return layout_inflater;
+	}
+
+	public CharSequence getTitle() {
+		return "Title";
+	}
+
 	private native void nativeFinish(long native_window);
 	private static native void nativeStartActivity(Activity activity);
 }

src/api-impl/android/app/DownloadManager.java

@@ -0,0 +1,5 @@
+package android.app;
+
+public class DownloadManager {
+	
+}

src/api-impl/android/app/Fragment.java

@@ -0,0 +1,5 @@
+package android.app;
+
+public class Fragment {
+	
+}

src/api-impl/android/app/FragmentManager.java

@@ -0,0 +1,16 @@
+package android.app;
+
+public class FragmentManager {
+	
+	public Fragment findFragmentByTag(String tag) {
+		return null;
+	}
+
+	public FragmentTransaction beginTransaction() {
+		return new FragmentTransaction();
+	}
+
+	public boolean executePendingTransactions() {
+		return false;
+	}
+}

src/api-impl/android/app/FragmentTransaction.java

@@ -0,0 +1,12 @@
+package android.app;
+
+public class FragmentTransaction {
+	
+	public FragmentTransaction add(Fragment fragment, String string) {
+		return this;
+	}
+
+	public int commit() {
+		return 0;
+	}
+}

src/api-impl/android/app/SearchManager.java

@@ -0,0 +1,5 @@
+package android.app;
+
+public class SearchManager {
+	
+}

src/api-impl/android/app/UiModeManager.java

@@ -0,0 +1,10 @@
+package android.app;
+
+import android.content.res.Configuration;
+
+public class UiModeManager {
+	
+	public int getCurrentModeType() {
+		return Configuration.UI_MODE_TYPE_NORMAL;
+	}
+}

src/api-impl/android/app/WallpaperManager.java

@@ -0,0 +1,5 @@
+package android.app;
+
+public class WallpaperManager {
+	
+}

src/api-impl/android/app/admin/DevicePolicyManager.java

@@ -0,0 +1,5 @@
+package android.app.admin;
+
+public class DevicePolicyManager {
+	
+}