Calendar: Added the read external storage permission for read media provider.

As "READ_EXTERNAL_STORAGE" permission is enforced starting in API level 19.
So we need add this permission to manifest for access the media provider to
get the ringtone's title.

CRs-Fixed: 643665

Change-Id: I3f5b76ff5e244932effb4bb2698ce15a83e77876
Calendar: Check if the duration is empty before parser it when delete the events

If the event end time is 0, it will calculate the end time by "duration"
string. But if the "duration" is null, it will lead the NullPointerException.

So check the duration string is empty or not before use it to get the end
time when delete the events.

CRs-Fixed: 650814

Change-Id: I97350db4103959b851367beae53f09200a2a29b8
Calendar: The delete events option status changed after rotate screen

Calendar through LoadManager to query the total number of events, and
update the delete events option status in onLoadFinished method. But
this method will be called at the first time load data or data have
changed, so can't update option status when rotating screen.

Calls the initLoader function in onCreate and onResume ensure that
the onLoadFinished can be callback.

CRs-Fixed: 650667

Change-Id: Id96f28bf648de374fb5d2cb7e0827e072f5342bd