Add initial 'Pulled' crate, change visual representation, etc.
* Add Helper script for running from Makefile (because of
the W^X protection used in OpenBSD).
* Add platform specific notes for OpenBSD.
* Add initial 'Pulled' crate.
* Fix 'slime.sh' helper script for OpenBSD.
* Change visual representation to allow more than
one visual for a crate. This is needed for example
in 'Pulled' crates where the "handles" can be
drawn with much fewer assets by allowing the
separation of the base crate from the different
visuals for the handles. This can be used in other
places too (for example counters and timers can
have the time from a separate visual).
* Update all existing visual representations to use
lists of identifiers (instead of scalar identifiers).
* Check for NIL in function 'on-which-side-is-other'