Replace md5 module with hashlib

fix following pylint error:

************* Module connectors.ConnectorBase
connectors/ConnectorBase.py:7: [W1648(bad-python3-import), ] Module moved in Python 3
************* Module runtime.PLCObject
runtime/PLCObject.py:33: [W1648(bad-python3-import), ] Module moved in Python 3

#!/usr/bin/env python
# -*- coding: utf-8 -*-

# See COPYING.Runtime file for copyrights details.

LogLevels = ["CRITICAL", "WARNING", "INFO", "DEBUG"]
LogLevelsCount = len(LogLevels)
LogLevelsDict = dict(zip(LogLevels, range(LogLevelsCount)))
LogLevelsDefault = LogLevelsDict["DEBUG"]