Added a ReadOnlyFill property

ReadOnlyFill property for when you want the control to be readonly, but
still want a custom colour showing rather than the default black.
Fixes Bug #47 - provides ability to tie into back button and optionally cancel form closing event
Added fix to avoid live tile flipping when only one item is availble
Merge pull request #178 from dotMorten/master

Don't animate live tile if Count =< 1
Modifications to dropdown sample for font variations
Merge branch 'dev' of https://github.com/timheuer/callisto into dev
Fix #167: Added listener for Window SizeChanged which should cause light dismiss surfaces to dismiss.
Fix #171: Enhancing flyout/IHM placement logic to adjust for more visible input areas in certain scenarios.
Merge https://github.com/lprichar/callisto into lprichar-master
Fix #47: Adding BackTapped event to be able to leverage
Fix #156: Changing 'tapped' to click so that it maps for touch and keyboard
Merge branch 'master' of https://github.com/ScottIsAFool/callisto into ScottIsAFool-master
Merging ReadOnlyFill for Rating control
Fix #136 by unsealing CustomDialog
Fix #140 Guard against if the parent is not a Flyout