Color and Accent Cleanups

-) Added AccentBrushes for all Accents and replaced where possible
(needed) in controls
-) Renamed BraindingBrush to ProgressBrush and changed gradient to
HighlightColor -> AccentColor3
-) Renamed HighlightDarkColor to HighlightColor (because they where
always the same and only HighlightDarkColor was used)
-) Commented unused Brushes out (HighlightLightBrush,
NavigationBorderBrush, NavigationForegroundBrush, PageBorderBrush,
BodyTextColorBrush, HoverHyperlinkForegroundBrush,
HoverHyperlinkBackgroundBrush, ItemSelectedBrush, SliderTrackBrush)
Brush Cleanups

-) Exchanged Colors with Brushes where possible
-) Use WhiteBrush and BlackBrush instead of WhiteColorBrush and
BlackColorBrush everywhere (majority already used it that way)
Removed AppBarButton, renamed colour to color

-) Removed AppBarButton.cs and .xaml
-) Renamed Colours.xaml to Color.xaml
-) Renamed all occurrences of colour to Color
Changed gray tones order
Merge pull request #3 from MahApps/master

Merge MahApps master
Merged Master
Merge pull request #5 from MahApps/master

Merge MahApps master...again
Merge branch 'master' into color-changes
Fixed misused ResourceDictionary name and grid
Merge pull request #688 from stefan-schweiger/color-changes

Color and Accent Cleanups