Fix validity time check for UFO pickle (mg5amcnlo#97)

* In models/import_ufo.py, include  models/import_ufo.py itself in the list of files to check pickle validity (see mg5amcnlo#89)

* In madgraph/iolibs/files.py, bug fix in pickle validity check: use getmtime instead of getctime (see mg5amcnlo#89)

* In models/import_ufo.py and madgraph/iolibs/files.py, remove debug printouts from the patch for mg5amcnlo#89

* In madgraph/iolibs/files.py, go back from getctime to getmtime in pickle validity check as suggested by Olivier, this is enough

* In models/import_ufo.py, use __file__ to include models/import_ufo.py itself in the list of files to check pickle validity (see mg5amcnlo#89)

models/import_ufo.py

@@ -349,6 +349,7 @@ def import_full_model(model_path, decay=False, prefix=''):
                 raise UFOImportError("%s directory is not a valid UFO model: \n %s is missing" % \
                                                          (model_path, filename))
         files_list.append(filepath)
+    files_list.append(__file__) # include models/import_ufo.py itself, see mg5amcnlo/mg5amcnlo#89
     # use pickle files if defined and up-to-date
     if aloha.unitary_gauge: 
         pickle_name = 'model.pkl'