Bug 881137 - hdpi/xhdpi resolution assets and layout for Calendar app

Update the image files as 1.5 times bigger images.
http://bugzil.la/881137

We removed clear@1.5x.png and checkmark@1.5x.png because these images is not provided from Patryck.
And we already created  a bug http://bugzil.la/890438 for getting these images.