Allow users to cancel each import/export.

- add cancel capability for vCard export.
- use jobId for Notification id, so that users can cancel each
  vCard import/export request.

Note:
As for Notification id, it may conflict with each other when
VCardService is shutdown.

Minor changes:
- add file name to each notification: users can see "xxx.vcf
  is successfully imported" instead of "vcard is successfully
  imported"
- rename mCancelled to mCanceled. strings.xml has "canceled",
  so inconsistent inside the app. Ignore the inconsistency
  between the spell in the app and Future#isCancelled().

Bug: 3215008
Change-Id: I7532e3d1b35a8bbeb694e47077554e36190482ed
diff --git a/AndroidManifest.xml b/AndroidManifest.xml
index 09d5a6e..56d9a02 100644
--- a/AndroidManifest.xml
+++ b/AndroidManifest.xml
@@ -544,7 +544,7 @@
             </intent-filter>
         </activity>
 
-        <activity android:name=".vcard.CancelImportActivity"
+        <activity android:name=".vcard.CancelActivity"
             android:theme="@style/BackgroundOnly" />
 
         <activity android:name=".vcard.SelectAccountActivity"