Machines conduct digilines above

Discussion on issue #194 was kinda left hanging unresolved.

There's some machines that should allow digiline connection from above, at least if connected with digiline cables.
At least supply converter.

Options I see here is to

• allow digiline connection above all machines.
• add custom rule for machines that are supposed to allow cable connection from above.
• find a way to allow different connection based on used cable, power cables have separate rules.
  Most common rule is {"bottom", "back", "left", "right"}
  Not sure if this is possible at all.

Also I want to remind people who were part of that discussion that

• Personally I am not against having this feature for all machines.
• I am against invalid reasoning like telling that it should be done because other things are broken.
• Question I had: "How likely it is that it causes problems with existing networks?"

  That said when I added custom digiline rules only reason why I did not want to add connection directly above was to avoid problems with excessive messages sent to digiline network where you do not expect those but other than that I'm not against adding connection from above.
  Just think how many problems it might cause with current networks in world, how many will contraptions would cause higher digiline usage (and added penalty if connection would be added)? Would it be low enough for it to be acceptable?

Start by reading issue #194 and the unresolved discussion here, then inspect how custom digiline connection rules and the supply converter are currently handled. Compare the proposed connection options and assess their effect on existing networks and message volume. Done requires a decided rule for above connections and agreement on which machines, if any, should support them.