fix ShowWindowCommandsOnTop for multiple opened flyouts
Merge pull request #1148 from MahApps/1145-punker76-ShowWindowCommandsOnTop-with-more-than-one-opened-flyout

fix ShowWindowCommandsOnTop for multiple opened flyouts
Improve RangeSlider mouse pressed handling. Now all previewmouse events handled by stackpanel.
Merge pull request #1152 from QuantumDeveloper/RangeSlider

RangeSlider V2.3