Enable Dark theme

TODO:
- fix the app freeze when user changes the app theme.

Riot/ViewController/ContactsTableViewController.m

@@ -104,6 +104,21 @@
 - (void)userInterfaceThemeDidChange
 {
     self.defaultBarTintColor = kRiotSecondaryBgColor;
+    self.barTitleColor = kRiotPrimaryTextColor;
+    
+    // Check the table view style to select its bg color.
+    self.contactsTableView.backgroundColor = ((self.contactsTableView.style == UITableViewStylePlain) ? kRiotPrimaryBgColor : kRiotSecondaryBgColor);
+    self.view.backgroundColor = self.contactsTableView.backgroundColor;
+    
+    if (self.contactsTableView.dataSource)
+    {
+        [self refreshContactsTable];
+    }
+}
+
+- (UIStatusBarStyle)preferredStatusBarStyle
+{
+    return kRiotDesignStatusBarStyle;
 }
 
 - (void)didReceiveMemoryWarning
@@ -197,8 +212,7 @@
     
     // In case of split view controller where the primary and secondary view controllers are displayed side-by-side on screen,
     // the selected room (if any) is updated and kept visible.
-    // Note: 'isCollapsed' property is available in UISplitViewController for iOS 8 and later.
-    if (self.splitViewController && (![self.splitViewController respondsToSelector:@selector(isCollapsed)] || !self.splitViewController.isCollapsed))
+    if (self.splitViewController && !self.splitViewController.isCollapsed)
     {
         [self refreshCurrentSelectedCell:YES];
     }
@@ -275,6 +289,29 @@
 
 #pragma mark - UITableView delegate
 
+- (void)tableView:(UITableView *)tableView willDisplayCell:(UITableViewCell *)cell forRowAtIndexPath:(NSIndexPath *)indexPath;
+{
+    cell.backgroundColor = kRiotPrimaryBgColor;
+    
+    // Update the selected background view
+    if (kRiotSelectedBgColor)
+    {
+        cell.selectedBackgroundView = [[UIView alloc] init];
+        cell.selectedBackgroundView.backgroundColor = kRiotSelectedBgColor;
+    }
+    else
+    {
+        if (tableView.style == UITableViewStylePlain)
+        {
+            cell.selectedBackgroundView = nil;
+        }
+        else
+        {
+            cell.selectedBackgroundView.backgroundColor = nil;
+        }
+    }
+}
+
 - (CGFloat)tableView:(UITableView *)tableView heightForHeaderInSection:(NSInteger)section
 {
     return [contactsDataSource heightForHeaderInSection:section];