Prepare Dark Theme

Remove the [UIApplication statusBarHidden] use (deprecated since iOS 9).
Use the default UIViewController-based status bar system.

Hide the user interface theme option in Settings.

https://github.com/vector-im/riot-meta/issues/22

Riot/ViewController/LanguagePickerViewController.m

@@ -18,6 +18,16 @@
 
 #import "AppDelegate.h"
 
+@interface LanguagePickerViewController ()
+{
+    /**
+     Observe kRiotDesignValuesDidChangeThemeNotification to handle user interface theme change.
+     */
+    id kRiotDesignValuesDidChangeThemeNotificationObserver;
+}
+
+@end
+
 @implementation LanguagePickerViewController
 
 - (void)finalizeInit
@@ -25,7 +35,6 @@
     [super finalizeInit];
 
     // Setup `MXKViewControllerHandling` properties
-    self.defaultBarTintColor = kRiotNavBarTintColor;
     self.enableBarTintColorStatusChange = NO;
     self.rageShakeManager = [RageShakeManager sharedManager];
 }
@@ -36,6 +45,30 @@
 
     // Hide line separators of empty cells
     self.tableView.tableFooterView = [[UIView alloc] init];
+    
+    // Observe user interface theme change.
+    kRiotDesignValuesDidChangeThemeNotificationObserver = [[NSNotificationCenter defaultCenter] addObserverForName:kRiotDesignValuesDidChangeThemeNotification object:nil queue:[NSOperationQueue mainQueue] usingBlock:^(NSNotification *notif) {
+        
+        [self userInterfaceThemeDidChange];
+        
+    }];
+    [self userInterfaceThemeDidChange];
+}
+
+- (void)userInterfaceThemeDidChange
+{
+    self.defaultBarTintColor = kRiotSecondaryBgColor;
+}
+
+- (void)destroy
+{
+    [super destroy];
+    
+    if (kRiotDesignValuesDidChangeThemeNotificationObserver)
+    {
+        [[NSNotificationCenter defaultCenter] removeObserver:kRiotDesignValuesDidChangeThemeNotificationObserver];
+        kRiotDesignValuesDidChangeThemeNotificationObserver = nil;
+    }
 }
 
 - (void)viewWillAppear:(BOOL)animated