use IdealForegroundColorBrush for title bar elements
Merge pull request #1611 from thoemmi/use-IdealForegroundColorBrush-in-title

use IdealForegroundColorBrush in title bar elements
Let the BaseMetroDialog inherit from ContentControl instead of Control

This way we don't have to duplicate the logic that a ContentControl already does for us
Merge pull request #1615 from MahApps/fix-dialog-databinding

Let the BaseMetroDialog inherit from ContentControl instead of Control