Merge branch '236-dark-navbar' into 'master'

Use dark navigation bar

See merge request !91

app/src/main/res/values/styles.xml

@@ -13,7 +13,7 @@
         <item name="android:windowBackground">@android:color/transparent</item>
         <item name="android:windowShowWallpaper">true</item>
         <item name="android:statusBarColor">@android:color/transparent</item>
-        <item name="android:navigationBarColor">#1affffff</item>
+        <item name="android:navigationBarColor">#26000000</item>
         <item name="android:windowDrawsSystemBarBackgrounds">true</item>
         <item name="android:enforceNavigationBarContrast">false</item>
         <item name="android:enforceStatusBarContrast">false</item>