ENH: Update ctkDICOMIndexer to report indexing time in seconds

For example:

```
"DICOM indexer has successfully processed 556 files [8.12s]"
```

Libs/DICOM/Core/ctkDICOMIndexer.cpp

@@ -130,6 +130,8 @@ void ctkDICOMIndexer::addListOfFiles(ctkDICOMDatabase& ctkDICOMDatabase,
                                      const QString& destinationDirectoryName)
 {
   Q_D(ctkDICOMIndexer);
+  QTime timeProbe;
+  timeProbe.start();
   d->Canceled = false;
   int CurrentFileIndex = 0;
   foreach(QString filePath, listOfFiles)
@@ -144,6 +146,11 @@ void ctkDICOMIndexer::addListOfFiles(ctkDICOMDatabase& ctkDICOMDatabase,
       break;
       }
   }
+  float elapsedTimeInSeconds = timeProbe.elapsed() / 1000.0;
+  qDebug()
+      << QString("DICOM indexer has successfully processed %1 files [%2s]")
+         .arg(CurrentFileIndex)
+         .arg(QString::number(elapsedTimeInSeconds,'f', 2));
   emit this->indexingComplete();
 }
 
@@ -171,6 +178,9 @@ bool ctkDICOMIndexer::addDicomdir(ctkDICOMDatabase& ctkDICOMDatabase,
   DcmDirectoryRecord* seriesRecord = NULL;
   DcmDirectoryRecord* fileRecord = NULL;
 
+  QTime timeProbe;
+  timeProbe.start();
+
   /*Iterate over all records in dicomdir and setup path to the dataset of the filerecord
   then insert. the filerecord into the database.
   If any UID is missing the record and all of it's subelements won't be added to the database*/
@@ -231,6 +241,11 @@ bool ctkDICOMIndexer::addDicomdir(ctkDICOMDatabase& ctkDICOMDatabase,
         }
       }
     }
+    float elapsedTimeInSeconds = timeProbe.elapsed() / 1000.0;
+    qDebug()
+        << QString("DICOM indexer has successfully processed DICOMDIR in %1 [%2s]")
+           .arg(directoryName)
+           .arg(QString::number(elapsedTimeInSeconds,'f', 2));
     emit foundFilesToIndex(listOfInstances.count());
     addListOfFiles(ctkDICOMDatabase,listOfInstances,destinationDirectoryName);
   }