mcpha: added two lines with meta data to histogram file

mcpha.py

@@ -684,12 +684,17 @@ class HstDisplay(QWidget, Ui_HstDisplay):
         try:
             dialog = QFileDialog(self, "Save hst file", path, "*.hst")
             dialog.setDefaultSuffix("hst")
-            name = "histogram-%s.hst" % time.strftime("%Y%m%d-%H%M%S")
+            timestamp = time.strftime("%Y%m%d-%H%M%S")
+            name = "histogram-%s.hst" % timestamp
             dialog.selectFile(name)
             dialog.setAcceptMode(QFileDialog.AcceptSave)
             if dialog.exec() == QDialog.Accepted:
                 name = dialog.selectedFiles()
-                np.savetxt(name[0], self.buffer, fmt="%u", newline=os.linesep)
+                np.savetxt(name[0],
+                           self.buffer,
+                           fmt="%u",
+                           header ='mcpha spectrum ' + timestamp + '\n counts per channel',
+                           newline=os.linesep)
                 self.log.print("histogram %d saved to file %s" % ((self.number + 1), name[0]))
         except:
             self.log.print("error: %s" % sys.exc_info()[1])