Modified system menu show behavior

The system menu usually opens when the right mouse button is released (except for the window icon). In this package the menu is shown when the right mouse button is pressed.
Add NumericUpDownChangedRoutedEventArgs in order to achieve the request in #1032

#Closes #1032
Changed to correct RoutedEvent
Added missing File
Oops, missed it in .net40
Merge pull request #1036 from xxMUROxx/hotfix/NumericUpDown

Add NumericUpDownChangedRoutedEventArgs...
corrected stretching of icons, fixes #1031
Update MetroAnimatedSingleRowTabControl.xaml

removing this margin, you can use TabStripMargin when the tabstripplacement is diferent of TOP!
Update MetroAnimatedTabControl.xaml

fix for metroanimatedtabcontrol
Update MetroTabControl.xaml

fix for the metrotabcontrol
Merge pull request #1042 from spiritdead/patch-5

MetroAnimatedSingleRowTabControl fix tabstripmargin
Merge pull request #1041 from thoemmi/issue1031-distorted-icons

corrected stretching of icons, fixes #1031
Merge pull request #1035 from Dotnetifier/patch-1

Modified system menu show behavior
Fixed an issue related to ToUpperConverter in the CleanWindow style. Added a glow to the CleanWindowDemo.
Fixes #1044
The GlowWindow was trying to update when it's host window's parent was trying to close the host window.
Fixes #954
Added support for ToggleButtons in WindowCommands and also modified WindowCommands code for supporting all ButtonBase controls.
Fixes #812
ProgressRing: In reality, people should just set IsActive to false if they are going to hide the control..... seriously.
MetroProgressBar: Stops trying to animate while the control is "invisible".
set visibility to hidden for invisible flayouts

set visibility for flyouts to hidden by default should improve
performance and a little bug if a flyout has left position (it's  a
short time visible if the main window has animation from right to left)
remove no longer required root measuring

i mean, we don't need this anymore, because we use ActualWidth and
ActualHeight of the root
ApplyAnimation only once before flyout shows