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

@@ -10,7 +10,10 @@
 #define VIVY_LOG_ERR(log)               VIVY_LOG_WITH_LEVEL(log, LogLevel::Error)
 #define VIVY_LOG_FATAL(log)             VIVY_LOG_WITH_LEVEL(log, LogLevel::Critical)
 
-#define VIVY_DCL_LOG_SINK(sink) std::shared_ptr<LogSink> sink{ LogSink::newSink() };
+#define VIVY_DCL_LOG_SINK(sink)                          \
+    std::shared_ptr<LogSink> sink{ LogSink::newSink() }; \
+    void flushLogSink() const noexcept { sink->flush(); }
+
 #define VIVY_DCL_LOG_DISPATCH(sink, name, dispatch) \
     std::shared_ptr<dispatch> name{ sink->newDispatcher<dispatch>() };