Added ability to enable metrics manager after it was disabled

Classes/BITHockeyManager.h

@@ -200,9 +200,7 @@
  will be turned off!
 
  Please note that the BITMetricsManager instance will be initialized anyway!
-
- @warning This property needs to be set before calling `startManager`
-
+
  *Default*: _NO_
  @see metricsManager
  */

Classes/BITHockeyManager.m

@@ -223,6 +223,13 @@ - (void)validateStartManagerIsInvoked {
   }
 }
 
+- (void)setDisableMetricsManager:(BOOL)disableMetricsManager {
+  if (self.metricsManager) {
+    self.metricsManager.disabled = disableMetricsManager;
+  }
+  _disableMetricsManager = disableMetricsManager;
+}
+
 - (void)setDisableFeedbackManager:(BOOL)disableFeedbackManager {
   if (self.feedbackManager) {
     [self.feedbackManager setDisableFeedbackManager:disableFeedbackManager];

Classes/Telemetry/BITMetricsManager.m

@@ -74,13 +74,12 @@ - (void)startManager {
 
 - (void)setDisabled:(BOOL)disabled {
   if (_disabled == disabled) { return; }
-
+    _disabled = disabled;
   if (disabled) {
     [self unregisterObservers];
   } else {
-    [self registerObservers];
+    [self startManager];
   }
-  _disabled = disabled;
 }
 
 #pragma mark - Sessions