Allow to choose between channel number and TOF

As requested by instrument scientists at ILL, this allows, when using the TOF loader, to choose between
having bins determined by time of flight values or by the bare channel number. Default is the latter.

Framework/DataHandling/inc/MantidDataHandling/LoadILLTOF2.h

@@ -70,6 +70,7 @@ private:
   static double calculateError(double in) { return sqrt(in); }
 
   API::MatrixWorkspace_sptr m_localWorkspace;
+  bool m_convertToTOF;
 
   std::string m_instrumentName = ""; ///< Name of the instrument
   std::string m_instrumentPath = ""; ///< Name of the instrument path

Framework/DataHandling/src/LoadILLTOF2.cpp

@@ -72,6 +72,7 @@ void LoadILLTOF2::init() {
   declareProperty(std::make_unique<WorkspaceProperty<>>("OutputWorkspace", "",
                                                         Direction::Output),
                   "The name to use for the output workspace");
+  declareProperty("convertToTOF", false, Direction::Input);
 }
 
 /**
@@ -80,6 +81,7 @@ void LoadILLTOF2::init() {
 void LoadILLTOF2::exec() {
   // Retrieve filename
   const std::string filenameData = getPropertyValue("Filename");
+  m_convertToTOF = getProperty("convertToTOF");
 
   // open the root node
   NeXus::NXRoot dataRoot(filenameData);
@@ -369,9 +371,15 @@ void LoadILLTOF2::loadDataIntoTheWorkSpace(
   // Put tof in an array
   auto &X0 = m_localWorkspace->mutableX(0);
   if (monitor.containsDataSet("time_of_flight")) {
-    for (size_t i = 0; i < m_numberOfChannels + 1; ++i) {
-      X0[i] = m_timeOfFlightDelay + m_channelWidth * static_cast<double>(i) -
-              m_channelWidth / 2; // to make sure the bin centre is correct
+    if (m_convertToTOF) {
+      for (size_t i = 0; i < m_numberOfChannels + 1; ++i) {
+        X0[i] = m_timeOfFlightDelay + m_channelWidth * static_cast<double>(i) -
+                m_channelWidth / 2; // to make sure the bin centre is correct
+      }
+    } else {
+      for (size_t i = 0; i < m_numberOfChannels + 1; ++i) {
+        X0[i] = static_cast<double>(i); // just take the channel index
+      }
     }
   } else {
     // Diffraction PANTHER