Resolve "Workflow execution tracking"

Closes #12 (closed)

Ewoks produces events with these fields:

Field	Type	Not None when	Value
host_name	str
process_id	int
user_name	str
job_id	str		random uuid by default
binding	str|None	using a scheduler
context	str		"workflow" or "node"
workflow_id	str
node_id	str|None	context == "node"
task_id	str|None	context == "node"
type	str		"start", "end" or "progress"
time	str		ISO 8601 format in local timezone
error	bool|None	event == "end"
error_message	str|None	event == "end"
error_traceback	str|None	event == "end"
progress	int|None	event == "progress"	number between 0 and 100
task_uri	str|None
input_uris	List[Dict]|None	event == "start"
output_uris	List[Dict]|None	event == "start"

• execinfo argument for execute_graph (job_id when a string). Same for the bindings.
• handler registration through ewokscore.events.add_handler
• handler registration through execinfo
• sqlite3 handler for testing
• emit task events (ewokscore)
• emit workflow events (ewokscore and all the bindings)
• execinfo CLI argument (including handler registration)

execinfo = {"job_id": ...,
            "handlers":[{"class": "ewokscore.events.handlers.EwoksSqlite3EventHandler",
                         "arguments": [{"name": "uri",
                                        "value": "file:/tmp/ewoks_event.db"}]}]