local-ize pretty muchg everything that was previously global except where
stuff needs to be globally-visible.  Also, fix a bad drop on valve.
local-ize a few more variables, move all of the nodebox models
into their own file and confine them and pretty much everything
else to the pipeworks.{} table (still global though).  More to
come.
default settings have to be global or pipeworks can't see them
(duh!)  confined them to pipeworks.{} table.
fix incorrect variable name
local-ize a few more functions
get rid of an excess print() call
local-ize a few more variables and functions
local-ize yet a few more variables
local-ize a few more variables
local-ize one last var
tube_item has to be global.  confined it to pipeworks.{} table.