Fix gaps shown when calendar size is not perfect.

Use a Repeater instead of GridView, and copy what QCalendarWidget does.

Change-Id: I2b734dbdee417be28c103cfa73ce34cd91319990
Reviewed-by: Jens Bache-Wiig <jens.bache-wiig@digia.com>
Reviewed-by: Mitch Curtis <mitch.curtis@digia.com>