Adjustments and fixes for attribute_wrapper merge
requested to merge 2021-04-02T17.33.12-branched_from_master-Adjustments_for_attribute_wrapper into master
- Added a prototype function mapping
- Improved exception formatting in some places
- Removed unneeded opcua import and import opcua where actually needed
- Correct the login in Initialise
- Correct the disconnect() call
- Ping server only if self.connected is True (now that I am thinking about it this modification could make this ping purposeless, please check)