Implement issue #1783881 (manifest option for adb-install-only apps)

You can now use android:testOnly="true" to not allow your .apk to be installed
as a normal app.  The only way to do so is with the pm command and giving the
-t option, which sets a new INSTALL_ALLOW_TEST flag when installing.

I also used this to clean up the install API...  actually, mostly to hide
it, since it is not accessible to apps so shouldn't be in the SDK.  We
will be doing some more work on it, so this will prevent adding yet
another backwards-compatibility-for-no-reason version.
diff --git a/core/java/android/content/pm/ApplicationInfo.java b/core/java/android/content/pm/ApplicationInfo.java
index fa9ec6e..88ac04c 100644
--- a/core/java/android/content/pm/ApplicationInfo.java
+++ b/core/java/android/content/pm/ApplicationInfo.java
@@ -126,6 +126,12 @@
     public static final int FLAG_TARGETS_SDK = 1<<8;
 
     /**
+     * Value for {@link #flags}: this is set of the application has set
+     * its android:targetSdkVersion to something >= the current SDK version.
+     */
+    public static final int FLAG_TEST_ONLY = 1<<9;
+
+    /**
      * Flags associated with the application.  Any combination of
      * {@link #FLAG_SYSTEM}, {@link #FLAG_DEBUGGABLE}, {@link #FLAG_HAS_CODE},
      * {@link #FLAG_PERSISTENT}, {@link #FLAG_FACTORY_TEST}, and