Move CInputManager from singleton to CApplication member

The main reason why CInputManager was singleton is the easy access across
the code. That had the negative side effect that time of destruction was
at a very late stage of the shutdown and could not be controlled by us.
My moving it to CApplication, the access is equally easy (using sApp) and
allows to be cleaned up properly during graceful shutdown.

ref T391

src/blackcore/inputmanager.cpp

@@ -30,12 +30,6 @@ namespace BlackCore
         reloadHotkeySettings();
     }
 
-    CInputManager *CInputManager::instance()
-    {
-        static CInputManager instance;
-        return &instance;
-    }
-
     void CInputManager::registerAction(const QString &action, const QPixmap &icon)
     {
         if (!m_availableActions.contains(action))