Theme system

Solves #1

Can choose between QtCreator's themes and base Vivy theme, or system's theme.

Depends on !21 (merged)

src/Lib/Log.hh

@@ -197,13 +197,6 @@ public:
         return dispatch;
     }
 
-    template <Derived<LogSinkDispatcher> DispatcherType, typename... Args>
-    DispatcherType *newUnmanagedDispatcher(Args &&...args) noexcept
-    {
-        DispatcherType *dispatch = new DispatcherType(std::forward<Args>(args)...);
-        return dispatch;
-    }
-
     std::shared_ptr<Logger> newLogger(const StringType auto &category) noexcept
     {
         std::shared_ptr<Logger> logger = std::make_shared<Logger>(this, category);