Removed HeaderFontSize-DP and used FontSize-DP in TabItem
Removed uncommented part
Merge pull request #680 from xxMUROxx/hotfix/FontSizeProperty-TabItem

Removed HeaderFontSize-DP and used FontSize-DP in TabItem
need this for #739
Merge branch 'origin/master' #680

Conflicts:
	samples/MetroDemo/MainWindow.xaml