Fetching flow executions

Few functions for fetching flow executions.
This creates an asymmetry between the first call to `self._refresh` (which has the password) and the later ones (which don't).

Since we now allow the password to be stored locally, I think it'd be cleaner to attach the password to the instance directly (i.e. have `self.password`) and use it in `self._refresh` if it exists. E.g. adding a line there like `password = password or self.password`.

This is not an issue in most cases currently (as remote session IDs live typically much longer than the local `Session` object) but could lead to strange behaviors otherwise.