consistency in case for file writing

Depending on the modes, the files written vary from PHASERTNG to phasertng:

    #modelfile = os.path.join(self.working_parameters.phasertng.suite.database, "PHASERTNG."+str(exp.tag)+"."+str(exp.identifier))
    modelfile = os.path.join(self.working_parameters.phasertng.suite.database,
                             "phasertng." + str(exp.tag) + "." + str(exp.identifier))