Dark mode support

Centralized all colors, tweaked application paletter in darkmode to make it darker.

pglab/main.cpp

@@ -1,8 +1,10 @@
 #include "MasterController.h"
+#include "util/Colors.h"
 #include <QApplication>
 #ifdef _WIN32
 # include <winsock2.h>
 #endif
+#include <QPalette>
 #include <memory>
 
 int main(int argc, char *argv[])
@@ -28,6 +30,8 @@ int main(int argc, char *argv[])
 	QCoreApplication::setOrganizationDomain("eelkeklein.nl");
 	QCoreApplication::setApplicationName("pglab");
 
+    InitApplicationPalette();
+
     int result = -1;
     {   
         // make sure the io_service is stopped before we wait on the future