refactor: initial migration to QuaZip 1.2

Let's move off our custom QuaZip. In the olden times we needed the
custom version of QuaZip, as it was basically unmaintained and on
SourceForge (eww). But nowadays it's maintained and on GitHub. See
new GitHub page: https://github.com/stachenov/quazip

launcher/modplatform/technic/SingleZipPackInstallTask.h

@@ -18,7 +18,7 @@
 #include "InstanceTask.h"
 #include "net/NetJob.h"
 
-#include "quazip.h"
+#include "QuaZip-Qt5-1.2/quazip/quazip.h"
 
 #include <QFutureWatcher>
 #include <QStringList>