Add a sample download dialog and upload sub-system

Samples are  downloaded from a  web server, currently the  SF download
server.   The samples  are  stored in  the  source controlled  samples
directory and the CMake script  there builds a suitable directory tree
for upload to the web  server under samples/web containing the samples
hierarchy and the  generated JSON contents database  file. The samples
CMake script also  defines an 'upload-samples' target  that uses rsync
to efficiently upload  the samples and the  accompanying contents JSON
database file.

Any directory structure under the samples directory may be created, to
add a new sample file simply add  the file to source control and amend
the list of sample files (SAMPLE_FILES) in samples/CMakeLists.txt.

git-svn-id: svn+ssh://svn.code.sf.net/p/wsjt/wsjt/branches/wsjtx@6308 ab8295b8-cf94-4d9e-aec4-7959e3be5d79

main.cpp

@@ -7,6 +7,7 @@
 
 #include <QDateTime>
 #include <QApplication>
+#include <QNetworkAccessManager>
 #include <QRegularExpression>
 #include <QObject>
 #include <QSettings>
@@ -206,7 +207,7 @@ int main(int argc, char *argv[])
                                            ).toBool () ? 1u : 4u;
       }
 
-      MainWindow w(multiple, &settings, &mem_jt9, downSampleFactor);
+      MainWindow w(multiple, &settings, &mem_jt9, downSampleFactor, new QNetworkAccessManager {&a});
       w.show();
 
       QObject::connect (&a, SIGNAL (lastWindowClosed()), &a, SLOT (quit()));