Perform initial refactoring work

Things that were once singletons are no longer singletons, but are
instead stored in the "Application" singleton

Some singletons still remain, and some renaming/renamespacing is left

src/widgets/split.hpp

@@ -43,9 +43,7 @@ class Split : public BaseWidget
     Q_OBJECT
 
 public:
-    explicit Split(SplitContainer *parent);
-    explicit Split(BaseWidget *widget);
-    explicit Split(singletons::ThemeManager &manager, QWidget *parent);
+    explicit Split(QWidget *parent);
     ~Split() override;
 
     pajlada::Signals::NoArgSignal channelChanged;
@@ -103,6 +101,8 @@ private:
     pajlada::Signals::Connection usermodeChangedConnection;
     pajlada::Signals::Connection indirectChannelChangedConnection;
 
+    std::vector<pajlada::Signals::ScopedConnection> managedConnections;
+
     void doOpenAccountPopupWidget(AccountPopupWidget *widget, QString user);
     void channelNameUpdated(const QString &newChannelName);
     void handleModifiers(QEvent *event, Qt::KeyboardModifiers modifiers);