validation text always white
fix wrong MetroWindow Background
#711 more accurate glow borders
#652 fix NullReferenceException in GlowWindow
Merge pull request #728 from MahApps/652-711-GlowWindow-issues

glow window issues
ActualWidth and ActualHeight instead DesiredSize
Merge pull request #729 from MahApps/726-punker76-Flyout-width

fix for #726 use ActualWidth and ActualHeight instead DesiredSize
from @xxMUROxx: set dpi factor to 1 as fallback
Add ClearButton for ComboBox
Merge pull request #730 from xxMUROxx/feature/ComboBoxClearButton

Add ClearButton for ComboBox
ComboBox style formatting
minor TextboxHelper changes