Colors cleanup

- removed mOutlineVariant, using mOutline everywhere
- reworked all predefined color schemes (dark mode only, light mode
incoming)

Assets/ColorScheme/Gruvbox.json

@@ -6,16 +6,13 @@
         "mOnSecondary": "#282828",
         "mTertiary": "#83a598",
         "mOnTertiary": "#282828",
-
         "mError": "#fb4934",
         "mOnError": "#282828",
-
         "mSurface": "#282828",
         "mOnSurface": "#fbf1c7",
         "mSurfaceVariant": "#3c3836",
         "mOnSurfaceVariant": "#ebdbb2",
-        "mOutline": "#665c54",
-        "mOutlineVariant": "#3c3836",
+        "mOutline": "#504945",
         "mShadow": "#282828"
     },
     "light": {
@@ -25,16 +22,13 @@
         "mOnSecondary": "#fbf1c7",
         "mTertiary": "#458588",
         "mOnTertiary": "#fbf1c7",
-
         "mError": "#cc241d",
         "mOnError": "#fbf1c7",
-
         "mSurface": "#fbf1c7",
         "mOnSurface": "#3c3836",
         "mSurfaceVariant": "#ebdbb2",
         "mOnSurfaceVariant": "#7c6f64",
-        "mOutline": "#928374",
-        "mOutlineVariant": "#bdae93",
+        "mOutline": "#bdae93",
         "mShadow": "#d5c4a1"
     }
 }