Always work with pointers to filters and subscriptions, drop the references for API consistency

shell/src/SubscriptionsCommand.cpp

 #include <iostream>
 #include <sstream>
 
 #include "SubscriptionsCommand.h"
 
 namespace
 {
   typedef std::vector<AdblockPlus::SubscriptionPtr> SubscriptionList;
 
   void ShowSubscriptionList(const SubscriptionList& subscriptions)
@@ skipping 60 matching lines @@
 }
 
 void SubscriptionsCommand::ShowSubscriptions()
 {
   ShowSubscriptionList(filterEngine.GetListedSubscriptions());
 }
 
 void SubscriptionsCommand::AddSubscription(const std::string& url,
                                            const std::string& title)
 {
-  AdblockPlus::Subscription& subscription = filterEngine.GetSubscription(url);
+  AdblockPlus::SubscriptionPtr subscription = filterEngine.GetSubscription(url);
   if (title.size())
-    subscription.SetProperty("title", title);
-  subscription.AddToList();
+    subscription->SetProperty("title", title);
+  subscription->AddToList();
 }
 
 void SubscriptionsCommand::RemoveSubscription(const std::string& url)
 {
-  AdblockPlus::Subscription& subscription = filterEngine.GetSubscription(url);
-  if (!subscription.IsListed())
+  AdblockPlus::SubscriptionPtr subscription = filterEngine.GetSubscription(url);
+  if (!subscription->IsListed())
   {
     std::cout << "No subscription with URL '" << url << "'" << std::endl;
     return;
   }
-  subscription.RemoveFromList();
+  subscription->RemoveFromList();
 }
 
 void SubscriptionsCommand::UpdateSubscriptions()
 {
   const SubscriptionList& subscriptions = filterEngine.GetListedSubscriptions();
   for (SubscriptionList::const_iterator it = subscriptions.begin();
        it != subscriptions.end(); it++)
     (*it)->UpdateFilters();
 }
 
 void SubscriptionsCommand::FetchSubscriptions()
 {
   filterEngine.FetchAvailableSubscriptions(&ShowSubscriptionList);
 }