Creates a new editor for the given parent and operator.
        
        :param      parent      | <QWidget>
                    operator    | <str>
                    value       | <variant>

def createEditor(self, parent, column, operator, value):
        """
        Creates a new editor for the given parent and operator.
        
        :param      parent      | <QWidget>
                    operator    | <str>
                    value       | <variant>
        """
        editor = super(NumericPlugin, self).createEditor(parent,
                                                         column,
                                                         operator,
                                                         value)
        
        if isinstance(editor, QLineEdit):
            validator = QRegExpValidator(QRegExp('^-?\d+\.?\d*'), editor)
            editor.setValidator(validator)
            if value is None:
                value = 0
            editor.setText(nativestring(value))
        return editor