Can set Handled for Increment/Decrement/ValueChanged

Closes #1075
Fixes #1079 - Dynamically changing flyout position doesn't work when flyout is open
Merge pull request #1076 from xxMUROxx/hotfix/NumericUpDown

Can set Handled for Increment/Decrement/ValueChanged
- Don't use 'IsOpen' as @punker76 suggested

- Added a property to Flyout: AnimateOnPositionChange (defaults to true)

This controls whether we animate the flyout when changing the 'Position' and it is already open.
Merge pull request #1080 from remcoros/master

Fixes #1079 - Dynamically changing flyout position doesn't work when fly...