Start on user manual
Change "altitude" to "elevation" in manual

Vanessa finds "altitude" to carry too much of an aviation connotation.
Zefram finds "elevation" to carry insufficient connotation of being
relative to sea level, so also adds a clarifying note.  Beware of changing
this terminology without negotiation, as it aroused surprisingly strong
opinions.
Fix stray British spellings in manual
More manual

Added sections on the technic-specific kinds of item processing, and on
generic metal mechanics, and the specific trickery around iron (merging
in notes_on_iron).
More manual

Sections on rubber and electrical power.
More manual

Added section on chests.  Fixed another stray British spelling.
Backslashed literal underscores to avoid them being interpreted as
emphasis markup.
Manual sectioning

Expand list of sections yet to be written.  Arrange sections both written
and unwritten into a two-level structure, with a bit of consequential
reordering.
Manual section on uranium enrichment
Administrative world anchor
Revise rules for regenerating latex

To ensure that only rubber tree trunk nodes that are part of trees
regenerate, rather than those that are used as building blocks, check
that they are sufficiently close to rubber tree leaves.  This replaces the
older rule that naturally-grown trunks regenerate (regardless of leaves)
and manually-placed trunks don't (even though manually building a tree
otherwise works).  The detection of manually-placed trunks was in any
case broken for users of moretrees, because that mod fails to set the
flag signalling manual placement.

Incidentally also fix a bug that caused rubber tree branches (horizontal
trunk nodes) to turn vertical when regenerating latex.  Rather than set
the complete node structure, only switch the type name, as does the tree
tap when emptying the node.