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
Modifications to dropdown sample for font variations
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.
Fix #47: Adding BackTapped event to be able to leverage
Fix #156: Changing 'tapped' to click so that it maps for touch and keyboard
Merging ReadOnlyFill for Rating control
Fix #136 by unsealing CustomDialog
Fix #140 Guard against if the parent is not a Flyout
Revising versions in deployable packages
Resolve issue #177: OAuthHelpers sample page

Adding an OAuthHelpers sample page.