* removed all the performance metric code into a separate function.
* restructured the code so it is either creating a new workflow, or deserializing an old one.
* Added code to upgrade serialized objects from 1.0 to 1.1
* Using the new method of creating a bpmn_workflow object:
```python
parser = self.get_spec_parser(self.spec_files, spec_info)
top_level = parser.get_spec(spec_info.primary_process_id)
subprocesses = parser.get_process_specs()
self.bpmn_workflow = BpmnWorkflow(top_level, subprocesses, script_engine=self._script_engine)
```
Fixed a few minor bugs that stood out while testing
1. when updating a workflow, we should check for a valid task BEFORE calling cancel_notify, which requires a valid task.
2. get_localtime - quick fix on the date parser - for python 3.9.
3. the start_workflow script would error out in a way that made it unclear which workflow was having the problem. Fixed the error.