Faulty implementation of blinker's signal.send()

[mrvisscher]

According to blinker's documentation the .send method expects the first argument to be the sender object. bw2data's implementation is inconsistent with the documentation and within itself.

For example in signals.py, the sender argument is omitted, meaning it will be set as None. This makes using the sender argument in blinker's .connect method impossible.

brightway2-data/bw2data/signals.py

Lines 249 to 253 in 4fd8e93

	if signal:
	signaleddataset_on_save.send(
	old=old,
	new=self,
	)

In project.py the project dataset is passed through the sender arg, which is of course not how it should be used. This again breaks blinkers .connect method and is inconsistent with the earlier example.

brightway2-data/bw2data/project.py

Line 374 in 4fd8e93

project_changed.send(self.dataset)

Blinkers documentation for reference: https://blinker.readthedocs.io/en/stable/#blinker.Signal.send