Add AnalyticsScreenTimer and track more screens.

Update Analytics with new methods in MXAnalyticsDelegate.

Riot/Modules/Rooms/DirectoryPicker/DirectoryServerPickerViewController.m

@@ -38,6 +38,9 @@
     // Observe kThemeServiceDidChangeThemeNotification to handle user interface theme change.
     id kThemeServiceDidChangeThemeNotificationObserver;
 }
+
+@property (nonatomic) AnalyticsScreenTimer *screenTimer;
+
 @end
 
 @implementation DirectoryServerPickerViewController
@@ -49,6 +52,8 @@
     // Setup `MXKViewControllerHandling` properties
     self.enableBarTintColorStatusChange = NO;
     self.rageShakeManager = [RageShakeManager sharedManager];
+    
+    self.screenTimer = [[AnalyticsScreenTimer alloc] initWithScreen:AnalyticsScreenSwitchDirectory];
 }
 
 - (void)destroy
@@ -155,6 +160,12 @@
     [dataSource loadData];
 }
 
+- (void)viewDidAppear:(BOOL)animated
+{
+    [super viewDidAppear:animated];
+    [self.screenTimer start];
+}
+
 - (void)viewWillDisappear:(BOOL)animated
 {
     if (kAppDelegateDidTapStatusBarNotificationObserver)
@@ -166,6 +177,12 @@
     [super viewWillDisappear:animated];
 }
 
+- (void)viewDidDisappear:(BOOL)animated
+{
+    [super viewDidDisappear:animated];
+    [self.screenTimer stop];
+}
+
 - (void)displayWithDataSource:(MXKDirectoryServersDataSource*)theDataSource
                    onComplete:(void (^)(id<MXKDirectoryServerCellDataStoring> cellData))onComplete;
 {