Update FlatSlider.xaml

User can define width of vertical slider / height of horizontal slider
First thing is first: Remove SizeToContent.
Oops, forgot something.
Breaking change: changed MessageDialogContainer to MetroDialogContainer.
Update Icons.xaml

Added the following icons:
appbar_bold
appbar_italic
appbar_underline
appbar_font
appbar_fontsize
appbar_fontsize_increase
appbar_fontsize_decrease
appbar_textcolor
appbar_marker
Update TransitioningContentControl.cs
Update MainWindow.xaml
Update MainWindow.xaml.cs
Added the InputDialog.
Fixed the accented color scheme's transparency by using HighlightBrush instead of AccentColorBrush (which has 80% transparency by design). If it ain't broken, don't fix it.
RequestClose is now RequestCloseAsync. It now works for dialogs inside of user-created MetroWindows too.
Added the ```UseAnimations``` setting.
Wat
Prevent entering invalid characters:
Now the user is not able to enter invalid characters to the NumericUpDown control.
An invalid character is defined as character other than:
* Positive/Negative sign (only if it is the first character)
* Number
* Decimal Seperator (only if there is none present)
Added listening to the Paste command.
If the pasted data is invalid then the command is canceled, otherwise applied to the NumericUpDown control.
Now if the focus for the NumericUpDown is lost then the value is only validated if the internal TextBox is modified by the user
Removed SetSilentValue method that has no effect than setting the value in a "non-silent" way
Removed CoerceMinimum method because this is already handled by the base class RangeBase.
Minimum will never be greather than Maximum and thus also the other case.
Removal of the background flashing when the Minimum/Maximum was reached.
Added DelayChanged event