This fixes several issues:
* More than one switching station could become active on large networks
- Switching stations now semi-permanently become disabled if another is present
- Power monitors have been added to replace the function of "slave" switching stations, to discourage overuse of switching stations
* Networks did not reliably "split" when cutting a cable
- I "may" have caused this issue, but I believe it is solved by this
* Machines did not run without a player near the switching station
- Active switching stations now forceload themselves, and free the forceloaded block if disabled, dug, or disconnected
- Machines are only loaded to run them (as before), so only one mapblock (or two if the bottom edge of the switching station is a mapblock boundary) is loaded
- Cables are still only loaded during a full network recalculation
The switching station and supply converter only semantically connect to
cables in particular directions. Make them visually connect only in
the matching directions. This is done by special-casing in the cable
update logic. If more irregular items arise in the future, or the
existing items start to need facedir logic, this should be generalised
into something like the connect_sides system for pneumatic tubes.
the first-seen tier for which the machine was registered. So the
switching station, which is uniquely registered for all tiers, would
only visually connect to LV cable when placed, not to MV or HV cable.
(It would function nevertheless, and cable would connect to the switching
station if placed later.) Change to consider all tiers. Incidentally
avoid a gratuitous iteration through all registered machines.