Add log information for dynafed activities/actions #981
Description
It would be useful for network management/operations (and for debugging) if elementsd were to log information about dynamic federation operations/proposals/voting/activations/epoch transitions/etc.
Default logging could be as terse as the existing UpdateTip (i.e., just enough information to indicate that something interesting occurred or is about to occur, but including some identifier that can be used to discern this particular event from some other previous/subsequent occurrence).
More verbose logging could include expanded details of events (e.g., peers participating, specific CPE info, proposed block-height of activations, epoch counts/identifiers, etc.).