Some servers running ubuntu in particular were reporting issues with teleport tubes not working.
On investigation, all tube entries were colliding as string.format("%d", ...)
was returning either -2^31 or 2^31-1 depending on system bit width,
causing hash entries to be overwritten.
This is possibly related to the use of C sprintf within lua.
Fix this by using %g instead to interpret as double without int conversion,
with a large enough number of digits such that all possible 2^48 values from
minetest.hash_node_position() can be correctly serialised.
* don't forceload the block of every single tube in the world on every item being send through any one of them
* cache file contents to avoid unnecessary reads on every single item send through a tp tube
* reduce redundant metadata and table lookups
* reduce write operations during the same changes to a file
still to do is a switch from an arraylist-table to a hashmap-table to make lookups and updates on the cache faster
Describe the two modes as "Send and Receive" and "Send only", rather
than the misleading "On" and "Off". Also make the mode toggle button
lag-resistant.
Previously, some tube types were named based on their function, and others
based on some arbitrarily-chosen material used in their construction,
with no meaningful system governing which was in each category. With this
change they are consistently named according to function. Naming style
is also made consistent in the wording that identifies tubes as such,
and in capitalisation.
