Add API to call to vold for mounting OBBs

* Unhide StorageService class; hide all the USB-related items

* Add application-visible API to StorageManager for OBB files

* Add class for parceling OBB info across binders (ObbInfo)

* Add a JNI glue class to libutils/ObbFile (ObbScanner)

* Add API to MountService to deal with calling into vold and checking
  permissions

Change-Id: I33ecf9606b8ff535f3a2ada83931da6bbef41cfd

core/java/com/android/internal/app/IMediaContainerService.aidl

@@ -19,6 +19,7 @@ package com.android.internal.app;
 import android.net.Uri;
 import android.os.ParcelFileDescriptor;
 import android.content.pm.PackageInfoLite;
+import android.content.res.ObbInfo;
 
 interface IMediaContainerService {
     String copyResourceToContainer(in Uri packageURI,
@@ -28,4 +29,5 @@ interface IMediaContainerService {
                 in ParcelFileDescriptor outStream);
     PackageInfoLite getMinimalPackageInfo(in Uri fileUri, int flags);
     boolean checkFreeStorage(boolean external, in Uri fileUri);
-}
+    ObbInfo getObbInfo(in Uri fileUri);
+}