At some point in September 2020, an overhaul of lux radiation
happened that doubled the amount of radiation that lux emitted,
which had a side effect of halving the amount of lux needed for
a ziprune. Restore it to intended functionality, for now.
In the longer run, it may make sense to add something like a
lux_power group that correlates with the actual power level in
the cobble and not the escaping radiation to decouple these.
Reusing lux_cobble is also possible, but it may be best to also
decouple it from cobble...
The effect was overly robust and had a tendency to lag some
systems badly, especially with the new accelerated zipping that
can produce particles up to 3x as fast.
Fix wrong rune order in determining priority, AND also fix
checking other runes for link selection after a segment has
already been selected for a given origin point.
Try to zip a player up to 3 segments in each jump,
accelerating ziplinks by up to 3x for paths that are
already loaded.
Reduce the number of sound points generated
along the path to 1 at each vertex instead of 4
along each segment, to compensate for the fact
that we're generating up to 3x as many particle
spawners and sound spots otherwise each time.
There appears to be a race cond between
network clients and server, where the server
can set_pos(), but then get_pos() the next
tick and find the client still has not yet
honored the teleport, which was breaking the
ziprune "can't walk >2m away without
losing energization" rule.
We can transiently fix this by storing the old
position along with the new one, and
allowing both. This won't survive a server
restart though, so in the long run we will
need a second cached pos in metadata.
